diff --git a/BUILD.gn b/BUILD.gn
index f4f81fe41f..81266ebb81 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -390,7 +390,6 @@ rtc_source_set("webrtc_common") {
   deps = [
     ":typedefs",
     "api:array_view",
-    "api:optional",
     "api/video:video_bitrate_allocation",
     "rtc_base:checks",
     "rtc_base:deprecation",
diff --git a/api/BUILD.gn b/api/BUILD.gn
index 4357947997..71c2ec39bc 100644
--- a/api/BUILD.gn
+++ b/api/BUILD.gn
@@ -257,9 +257,9 @@ rtc_source_set("simulated_network_api") {
     "test/simulated_network.h",
   ]
   deps = [
-    ":optional",
     "../rtc_base:criticalsection",
     "../rtc_base:rtc_base",
+    "//third_party/abseil-cpp/absl/types:optional",
   ]
 }
 
@@ -286,18 +286,6 @@ rtc_source_set("array_view") {
   ]
 }
 
-# TODO(bugs.webrtc.org/9078): Deprecated, replaced by absl/types:optional.
-# Delete after webrtc and downstreams users are updated.
-rtc_source_set("optional") {
-  visibility = [ "*" ]
-  sources = [
-    "optional.h",
-  ]
-  deps = [
-    "//third_party/abseil-cpp/absl/types:optional",
-  ]
-}
-
 rtc_source_set("refcountedbase") {
   visibility = [ "*" ]
   sources = [
@@ -477,10 +465,6 @@ if (rtc_include_tests) {
 
     sources = [
       "array_view_unittest.cc",
-
-      # TODO(bugs.webrtc.org/8821): Remove optional_unittests when webrtc starts
-      # running absl unittest on each commit.
-      "optional_unittest.cc",
       "ortc/mediadescription_unittest.cc",
       "ortc/sessiondescription_unittest.cc",
       "rtcerror_unittest.cc",
@@ -496,7 +480,6 @@ if (rtc_include_tests) {
       ":array_view",
       ":libjingle_peerconnection_api",
       ":libjingle_peerconnection_test_api",
-      ":optional",
       ":ortc_api",
       "../rtc_base:checks",
       "../rtc_base:rtc_base_approved",
diff --git a/api/optional.h b/api/optional.h
deleted file mode 100644
index eada13fa9b..0000000000
--- a/api/optional.h
+++ /dev/null
@@ -1,27 +0,0 @@
-/*
- *  Copyright 2015 The WebRTC Project Authors. All rights reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree. An additional intellectual property rights grant can be found
- *  in the file PATENTS.  All contributing project authors may
- *  be found in the AUTHORS file in the root of the source tree.
- */
-
-// TODO(bugs.webrtc.org/9078): Use absl::optional directly.
-#ifndef API_OPTIONAL_H_
-#define API_OPTIONAL_H_
-
-#include "absl/types/optional.h"
-
-namespace rtc {
-
-using absl::nullopt_t;
-using absl::nullopt;
-
-template <typename T>
-using Optional = absl::optional<T>;
-
-}  // namespace rtc
-
-#endif  // API_OPTIONAL_H_
diff --git a/api/optional_unittest.cc b/api/optional_unittest.cc
deleted file mode 100644
index f56dc6d7ac..0000000000
--- a/api/optional_unittest.cc
+++ /dev/null
@@ -1,906 +0,0 @@
-/*
- *  Copyright 2015 The WebRTC Project Authors. All rights reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree. An additional intellectual property rights grant can be found
- *  in the file PATENTS.  All contributing project authors may
- *  be found in the AUTHORS file in the root of the source tree.
- */
-
-// TODO(bugs.webrtc.org/8821): Delete this file when absl unittests run on
-// webrtc bots.
-
-#include <memory>
-#include <sstream>
-#include <string>
-#include <utility>
-#include <vector>
-
-#include "api/optional.h"
-#include "rtc_base/gunit.h"
-
-namespace rtc {
-
-namespace {
-
-struct MyUnprintableType {
-  int value;
-};
-
-struct MyPrintableType {
-  int value;
-};
-
-struct MyOstreamPrintableType {
-  int value;
-};
-
-void PrintTo(const MyPrintableType& mpt, std::ostream* os) {
-  *os << "The value is " << mpt.value;
-}
-
-std::ostream& operator<<(std::ostream& os, const MyPrintableType& mpt) {
-  os << mpt.value;
-  return os;
-}
-
-std::ostream& operator<<(std::ostream& os, const MyOstreamPrintableType& mpt) {
-  os << mpt.value;
-  return os;
-}
-
-// Class whose instances logs various method calls (constructor, destructor,
-// etc.). Each instance has a unique ID (a simple global sequence number) and
-// an origin ID. When a copy is made, the new object gets a fresh ID but copies
-// the origin ID from the original. When a new Logger is created from scratch,
-// it gets a fresh ID, and the origin ID is the same as the ID (default
-// constructor) or given as an argument (explicit constructor).
-class Logger {
- public:
-  Logger() : id_(g_next_id++), origin_(id_) { Log("default constructor"); }
-  explicit Logger(int origin) : id_(g_next_id++), origin_(origin) {
-    Log("explicit constructor");
-  }
-  Logger(int origin, const Logger& pass_by_ref, Logger pass_by_value)
-      : id_(g_next_id++), origin_(origin) {
-    Log("multi parameter constructor");
-  }
-  Logger(const Logger& other) : id_(g_next_id++), origin_(other.origin_) {
-    LogFrom("copy constructor", other);
-  }
-  Logger(Logger&& other) : id_(g_next_id++), origin_(other.origin_) {
-    LogFrom("move constructor", other);
-  }
-  ~Logger() { Log("destructor"); }
-  Logger& operator=(const Logger& other) {
-    origin_ = other.origin_;
-    LogFrom("operator= copy", other);
-    return *this;
-  }
-  Logger& operator=(Logger&& other) {
-    origin_ = other.origin_;
-    LogFrom("operator= move", other);
-    return *this;
-  }
-  friend void swap(Logger& a, Logger& b) {
-    using std::swap;
-    swap(a.origin_, b.origin_);
-    Log2("swap", a, b);
-  }
-  friend bool operator==(const Logger& a, const Logger& b) {
-    Log2("operator==", a, b);
-    return a.origin_ == b.origin_;
-  }
-  friend bool operator!=(const Logger& a, const Logger& b) {
-    Log2("operator!=", a, b);
-    return a.origin_ != b.origin_;
-  }
-  void Foo() { Log("Foo()"); }
-  void Foo() const { Log("Foo() const"); }
-  static std::unique_ptr<std::vector<std::string>> Setup() {
-    std::unique_ptr<std::vector<std::string>> s(new std::vector<std::string>);
-    g_log = s.get();
-    g_next_id = 0;
-    return s;
-  }
-
- private:
-  int id_;
-  int origin_;
-  static std::vector<std::string>* g_log;
-  static int g_next_id;
-  void Log(const char* msg) const {
-    std::ostringstream oss;
-    oss << id_ << ':' << origin_ << ". " << msg;
-    g_log->push_back(oss.str());
-  }
-  void LogFrom(const char* msg, const Logger& other) const {
-    std::ostringstream oss;
-    oss << id_ << ':' << origin_ << ". " << msg << " (from " << other.id_ << ':'
-        << other.origin_ << ")";
-    g_log->push_back(oss.str());
-  }
-  static void Log2(const char* msg, const Logger& a, const Logger& b) {
-    std::ostringstream oss;
-    oss << msg << ' ' << a.id_ << ':' << a.origin_ << ", " << b.id_ << ':'
-        << b.origin_;
-    g_log->push_back(oss.str());
-  }
-};
-
-std::vector<std::string>* Logger::g_log = nullptr;
-int Logger::g_next_id = 0;
-
-// Append all the other args to the vector pointed to by the first arg.
-template <typename T>
-void VectorAppend(std::vector<T>* v) {}
-template <typename T, typename... Ts>
-void VectorAppend(std::vector<T>* v, const T& e, Ts... es) {
-  v->push_back(e);
-  VectorAppend(v, es...);
-}
-
-// Create a vector of strings. Because we're not allowed to use
-// std::initializer_list.
-template <typename... Ts>
-std::vector<std::string> V(Ts... es) {
-  std::vector<std::string> strings;
-  VectorAppend(&strings, static_cast<std::string>(es)...);
-  return strings;
-}
-
-}  // namespace
-
-TEST(OptionalTest, TestConstructDefault) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x;
-    EXPECT_FALSE(x);
-    EXPECT_FALSE(x.has_value());
-  }
-  EXPECT_EQ(V(), *log);
-}
-
-TEST(OptionalTest, TestConstructNullopt) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x(nullopt);
-    EXPECT_FALSE(x);
-    EXPECT_FALSE(x.has_value());
-  }
-  EXPECT_EQ(V(), *log);
-}
-
-TEST(OptionalTest, TestConstructCopyEmpty) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x;
-    EXPECT_FALSE(x);
-    EXPECT_FALSE(x.has_value());
-    auto y = x;
-    EXPECT_FALSE(y);
-    EXPECT_FALSE(y.has_value());
-  }
-  EXPECT_EQ(V(), *log);
-}
-
-TEST(OptionalTest, TestConstructCopyFull) {
-  auto log = Logger::Setup();
-  {
-    Logger a;
-    Optional<Logger> x(a);
-    EXPECT_TRUE(x);
-    EXPECT_TRUE(x.has_value());
-    log->push_back("---");
-    auto y = x;
-    EXPECT_TRUE(y);
-    EXPECT_TRUE(y.has_value());
-    log->push_back("---");
-  }
-  EXPECT_EQ(V("0:0. default constructor", "1:0. copy constructor (from 0:0)",
-              "---", "2:0. copy constructor (from 1:0)", "---",
-              "2:0. destructor", "1:0. destructor", "0:0. destructor"),
-            *log);
-}
-
-TEST(OptionalTest, TestConstructMoveEmpty) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x;
-    EXPECT_FALSE(x);
-    EXPECT_FALSE(x.has_value());
-    auto y = std::move(x);
-    EXPECT_FALSE(y);
-    EXPECT_FALSE(y.has_value());
-  }
-  EXPECT_EQ(V(), *log);
-}
-
-TEST(OptionalTest, TestConstructMoveFull) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x(Logger(17));
-    EXPECT_TRUE(x);
-    EXPECT_TRUE(x.has_value());
-    log->push_back("---");
-    auto y = std::move(x);
-    EXPECT_TRUE(x);
-    EXPECT_TRUE(x.has_value());
-    EXPECT_TRUE(y);
-    EXPECT_TRUE(y.has_value());
-    log->push_back("---");
-  }
-  EXPECT_EQ(
-      V("0:17. explicit constructor", "1:17. move constructor (from 0:17)",
-        "0:17. destructor", "---", "2:17. move constructor (from 1:17)", "---",
-        "2:17. destructor", "1:17. destructor"),
-      *log);
-}
-
-TEST(OptionalTest, TestCopyAssignToEmptyFromEmpty) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x, y;
-    x = y;
-  }
-  EXPECT_EQ(V(), *log);
-}
-
-TEST(OptionalTest, TestCopyAssignToFullFromEmpty) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x(Logger(17));
-    Optional<Logger> y;
-    log->push_back("---");
-    x = y;
-    log->push_back("---");
-  }
-  EXPECT_EQ(
-      V("0:17. explicit constructor", "1:17. move constructor (from 0:17)",
-        "0:17. destructor", "---", "1:17. destructor", "---"),
-      *log);
-}
-
-TEST(OptionalTest, TestCopyAssignToFullFromNullopt) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x(Logger(17));
-    log->push_back("---");
-    x = nullopt;
-    log->push_back("---");
-    EXPECT_FALSE(x);
-  }
-  EXPECT_EQ(
-      V("0:17. explicit constructor", "1:17. move constructor (from 0:17)",
-        "0:17. destructor", "---", "1:17. destructor", "---"),
-      *log);
-}
-
-TEST(OptionalTest, TestCopyAssignToFullFromEmptyBraces) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x(Logger(17));
-    log->push_back("---");
-    x = {};
-    log->push_back("---");
-    EXPECT_FALSE(x);
-  }
-  EXPECT_EQ(
-      V("0:17. explicit constructor", "1:17. move constructor (from 0:17)",
-        "0:17. destructor", "---", "1:17. destructor", "---"),
-      *log);
-}
-
-TEST(OptionalTest, TestCopyAssignToEmptyFromFull) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x;
-    Optional<Logger> y(Logger(17));
-    log->push_back("---");
-    x = y;
-    log->push_back("---");
-  }
-  EXPECT_EQ(
-      V("0:17. explicit constructor", "1:17. move constructor (from 0:17)",
-        "0:17. destructor", "---", "2:17. copy constructor (from 1:17)", "---",
-        "1:17. destructor", "2:17. destructor"),
-      *log);
-}
-
-TEST(OptionalTest, TestCopyAssignToFullFromFull) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x(Logger(17));
-    Optional<Logger> y(Logger(42));
-    log->push_back("---");
-    x = y;
-    log->push_back("---");
-  }
-  EXPECT_EQ(
-      V("0:17. explicit constructor", "1:17. move constructor (from 0:17)",
-        "0:17. destructor", "2:42. explicit constructor",
-        "3:42. move constructor (from 2:42)", "2:42. destructor", "---",
-        "1:42. operator= copy (from 3:42)", "---", "3:42. destructor",
-        "1:42. destructor"),
-      *log);
-}
-
-TEST(OptionalTest, TestCopyAssignToEmptyFromT) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x;
-    Logger y(17);
-    log->push_back("---");
-    x = Optional<Logger>(y);
-    log->push_back("---");
-  }
-  EXPECT_EQ(V("0:17. explicit constructor", "---",
-              "1:17. copy constructor (from 0:17)",
-              "2:17. move constructor (from 1:17)", "1:17. destructor", "---",
-              "0:17. destructor", "2:17. destructor"),
-            *log);
-}
-
-TEST(OptionalTest, TestCopyAssignToFullFromT) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x(Logger(17));
-    Logger y(42);
-    log->push_back("---");
-    x = Optional<Logger>(y);
-    log->push_back("---");
-  }
-  EXPECT_EQ(
-      V("0:17. explicit constructor", "1:17. move constructor (from 0:17)",
-        "0:17. destructor", "2:42. explicit constructor", "---",
-        "3:42. copy constructor (from 2:42)",
-        "1:42. operator= move (from 3:42)", "3:42. destructor", "---",
-        "2:42. destructor", "1:42. destructor"),
-      *log);
-}
-
-TEST(OptionalTest, TestMoveAssignToEmptyFromEmpty) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x, y;
-    x = std::move(y);
-  }
-  EXPECT_EQ(V(), *log);
-}
-
-TEST(OptionalTest, TestMoveAssignToFullFromEmpty) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x(Logger(17));
-    Optional<Logger> y;
-    log->push_back("---");
-    x = std::move(y);
-    log->push_back("---");
-  }
-  EXPECT_EQ(
-      V("0:17. explicit constructor", "1:17. move constructor (from 0:17)",
-        "0:17. destructor", "---", "1:17. destructor", "---"),
-      *log);
-}
-
-TEST(OptionalTest, TestMoveAssignToEmptyFromFull) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x;
-    Optional<Logger> y(Logger(17));
-    log->push_back("---");
-    x = std::move(y);
-    log->push_back("---");
-  }
-  EXPECT_EQ(
-      V("0:17. explicit constructor", "1:17. move constructor (from 0:17)",
-        "0:17. destructor", "---", "2:17. move constructor (from 1:17)", "---",
-        "1:17. destructor", "2:17. destructor"),
-      *log);
-}
-
-TEST(OptionalTest, TestMoveAssignToFullFromFull) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x(Logger(17));
-    Optional<Logger> y(Logger(42));
-    log->push_back("---");
-    x = std::move(y);
-    log->push_back("---");
-  }
-  EXPECT_EQ(
-      V("0:17. explicit constructor", "1:17. move constructor (from 0:17)",
-        "0:17. destructor", "2:42. explicit constructor",
-        "3:42. move constructor (from 2:42)", "2:42. destructor", "---",
-        "1:42. operator= move (from 3:42)", "---", "3:42. destructor",
-        "1:42. destructor"),
-      *log);
-}
-
-TEST(OptionalTest, TestMoveAssignToEmptyFromT) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x;
-    Logger y(17);
-    log->push_back("---");
-    x = Optional<Logger>(std::move(y));
-    log->push_back("---");
-  }
-  EXPECT_EQ(V("0:17. explicit constructor", "---",
-              "1:17. move constructor (from 0:17)",
-              "2:17. move constructor (from 1:17)", "1:17. destructor", "---",
-              "0:17. destructor", "2:17. destructor"),
-            *log);
-}
-
-TEST(OptionalTest, TestMoveAssignToFullFromT) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x(Logger(17));
-    Logger y(42);
-    log->push_back("---");
-    x = Optional<Logger>(std::move(y));
-    log->push_back("---");
-  }
-  EXPECT_EQ(
-      V("0:17. explicit constructor", "1:17. move constructor (from 0:17)",
-        "0:17. destructor", "2:42. explicit constructor", "---",
-        "3:42. move constructor (from 2:42)",
-        "1:42. operator= move (from 3:42)", "3:42. destructor", "---",
-        "2:42. destructor", "1:42. destructor"),
-      *log);
-}
-
-TEST(OptionalTest, TestResetEmpty) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x;
-    x.reset();
-  }
-  EXPECT_EQ(V(), *log);
-}
-
-TEST(OptionalTest, TestResetFull) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x(Logger(17));
-    log->push_back("---");
-    x.reset();
-    log->push_back("---");
-  }
-  EXPECT_EQ(
-      V("0:17. explicit constructor", "1:17. move constructor (from 0:17)",
-        "0:17. destructor", "---", "1:17. destructor", "---"),
-      *log);
-}
-
-TEST(OptionalTest, TestEmplaceEmptyWithExplicit) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x;
-    log->push_back("---");
-    x.emplace(42);
-    log->push_back("---");
-  }
-  // clang-format off
-  EXPECT_EQ(V("---",
-              "0:42. explicit constructor",
-              "---",
-              "0:42. destructor"),
-            *log);
-  // clang-format on
-}
-
-TEST(OptionalTest, TestEmplaceEmptyWithMultipleParameters) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x;
-    Logger ref(21);
-    Logger value(35);
-    log->push_back("---");
-    x.emplace(42, ref, std::move(value));
-    log->push_back("---");
-  }
-  // clang-format off
-  EXPECT_EQ(V("0:21. explicit constructor",
-              "1:35. explicit constructor",
-              "---",
-              "2:35. move constructor (from 1:35)",
-              "3:42. multi parameter constructor",
-              "2:35. destructor",
-              "---",
-              "1:35. destructor",
-              "0:21. destructor",
-              "3:42. destructor"),
-            *log);
-  // clang-format on
-}
-
-TEST(OptionalTest, TestEmplaceEmptyWithCopy) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x;
-    Logger y(42);
-    log->push_back("---");
-    x.emplace(y);
-    log->push_back("---");
-  }
-  // clang-format off
-  EXPECT_EQ(V("0:42. explicit constructor",
-              "---",
-              "1:42. copy constructor (from 0:42)",
-              "---",
-              "0:42. destructor",
-              "1:42. destructor"),
-            *log);
-  // clang-format on
-}
-
-TEST(OptionalTest, TestEmplaceEmptyWithMove) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x;
-    Logger y(42);
-    log->push_back("---");
-    x.emplace(std::move(y));
-    log->push_back("---");
-  }
-  // clang-format off
-  EXPECT_EQ(V("0:42. explicit constructor",
-              "---",
-              "1:42. move constructor (from 0:42)",
-              "---",
-              "0:42. destructor",
-              "1:42. destructor"),
-            *log);
-  // clang-format on
-}
-
-TEST(OptionalTest, TestEmplaceFullWithExplicit) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x(Logger(17));
-    log->push_back("---");
-    x.emplace(42);
-    log->push_back("---");
-  }
-  // clang-format off
-  EXPECT_EQ(
-      V("0:17. explicit constructor",
-        "1:17. move constructor (from 0:17)",
-        "0:17. destructor",
-        "---",
-        "1:17. destructor",
-        "2:42. explicit constructor",
-        "---",
-        "2:42. destructor"),
-      *log);
-  // clang-format on
-}
-
-TEST(OptionalTest, TestEmplaceFullWithMultipleParameters) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x(Logger(17));
-    Logger ref(21);
-    Logger value(35);
-    log->push_back("---");
-    x.emplace(42, ref, std::move(value));
-    log->push_back("---");
-  }
-  // clang-format off
-  EXPECT_EQ(V("0:17. explicit constructor",
-              "1:17. move constructor (from 0:17)",
-              "0:17. destructor",
-              "2:21. explicit constructor",
-              "3:35. explicit constructor",
-              "---",
-              "1:17. destructor",
-              "4:35. move constructor (from 3:35)",
-              "5:42. multi parameter constructor",
-              "4:35. destructor",
-              "---",
-              "3:35. destructor",
-              "2:21. destructor",
-              "5:42. destructor"),
-            *log);
-  // clang-format on
-}
-
-TEST(OptionalTest, TestEmplaceFullWithCopy) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x(Logger(17));
-    Logger y(42);
-    log->push_back("---");
-    x.emplace(y);
-    log->push_back("---");
-  }
-  // clang-format off
-  EXPECT_EQ(V("0:17. explicit constructor",
-              "1:17. move constructor (from 0:17)",
-              "0:17. destructor",
-              "2:42. explicit constructor",
-              "---",
-              "1:17. destructor",
-              "3:42. copy constructor (from 2:42)",
-              "---",
-              "2:42. destructor",
-              "3:42. destructor"),
-           *log);
-  // clang-format on
-}
-
-TEST(OptionalTest, TestEmplaceFullWithMove) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x(Logger(17));
-    Logger y(42);
-    log->push_back("---");
-    x.emplace(std::move(y));
-    log->push_back("---");
-  }
-  // clang-format off
-  EXPECT_EQ(V("0:17. explicit constructor",
-              "1:17. move constructor (from 0:17)",
-              "0:17. destructor",
-              "2:42. explicit constructor",
-              "---",
-              "1:17. destructor",
-              "3:42. move constructor (from 2:42)",
-              "---",
-              "2:42. destructor",
-              "3:42. destructor"),
-            *log);
-  // clang-format on
-}
-
-TEST(OptionalTest, TestDereference) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x(Logger(42));
-    const auto& y = x;
-    log->push_back("---");
-    x->Foo();
-    y->Foo();
-    std::move(x)->Foo();
-    std::move(y)->Foo();
-    log->push_back("---");
-    (*x).Foo();
-    (*y).Foo();
-    (*std::move(x)).Foo();
-    (*std::move(y)).Foo();
-    log->push_back("---");
-    x.value().Foo();
-    y.value().Foo();
-    std::move(x).value().Foo();
-    std::move(y).value().Foo();
-    log->push_back("---");
-  }
-  // clang-format off
-  EXPECT_EQ(V("0:42. explicit constructor",
-              "1:42. move constructor (from 0:42)",
-              "0:42. destructor",
-              "---",
-              "1:42. Foo()",
-              "1:42. Foo() const",
-              "1:42. Foo()",
-              "1:42. Foo() const",
-              "---",
-              "1:42. Foo()",
-              "1:42. Foo() const",
-              "1:42. Foo()",
-              "1:42. Foo() const",
-              "---",
-              "1:42. Foo()",
-              "1:42. Foo() const",
-              "1:42. Foo()",
-              "1:42. Foo() const",
-              "---",
-              "1:42. destructor"),
-            *log);
-  // clang-format on
-}
-
-TEST(OptionalTest, TestDereferenceWithDefault) {
-  auto log = Logger::Setup();
-  const Logger a(17), b(42);
-  Optional<Logger> x(a);
-  Optional<Logger> y;
-  EXPECT_EQ(a, x.value_or(Logger(42)));
-  EXPECT_EQ(b, y.value_or(Logger(42)));
-  EXPECT_EQ(a, Optional<Logger>(Logger(17)).value_or(b));
-  EXPECT_EQ(b, Optional<Logger>().value_or(b));
-  // Can't expect exact list of constructors and destructors because it is
-  // compiler-dependent. i.e. msvc produce different output than clang. Calls
-  // above are subject to copy elision that allow to change behavior.
-}
-
-TEST(OptionalTest, TestEquality) {
-  auto log = Logger::Setup();
-  {
-    Logger a(17), b(42);
-    Optional<Logger> ma1(a), ma2(a), mb(b), me1, me2;
-    log->push_back("---");
-    EXPECT_EQ(ma1, ma1);
-    EXPECT_EQ(ma1, ma2);
-    EXPECT_NE(ma1, mb);
-    EXPECT_NE(ma1, me1);
-    EXPECT_EQ(me1, me1);
-    EXPECT_EQ(me1, me2);
-    log->push_back("---");
-  }
-  EXPECT_EQ(
-      V("0:17. explicit constructor", "1:42. explicit constructor",
-        "2:17. copy constructor (from 0:17)",
-        "3:17. copy constructor (from 0:17)",
-        "4:42. copy constructor (from 1:42)", "---", "operator== 2:17, 2:17",
-        "operator== 2:17, 3:17", "operator!= 2:17, 4:42", "---",
-        "4:42. destructor", "3:17. destructor", "2:17. destructor",
-        "1:42. destructor", "0:17. destructor"),
-      *log);
-}
-
-TEST(OptionalTest, TestEqualityWithNullopt) {
-  auto log = Logger::Setup();
-  {
-    Logger a(17);
-    Optional<Logger> ma(a), me;
-    // Using operator== and operator!= explicitly instead of EXPECT_EQ/EXPECT_NE
-    // macros because those operators are under test.
-    log->push_back("---");
-
-    EXPECT_FALSE(ma == nullopt);
-    EXPECT_FALSE(nullopt == ma);
-    EXPECT_TRUE(me == nullopt);
-    EXPECT_TRUE(nullopt == me);
-
-    EXPECT_TRUE(ma != nullopt);
-    EXPECT_TRUE(nullopt != ma);
-    EXPECT_FALSE(me != nullopt);
-    EXPECT_FALSE(nullopt != me);
-
-    log->push_back("---");
-  }
-  // clang-format off
-  EXPECT_EQ(V("0:17. explicit constructor",
-              "1:17. copy constructor (from 0:17)",
-              "---",
-              // No operators should be called when comparing to empty.
-              "---",
-              "1:17. destructor",
-              "0:17. destructor"),
-            *log);
-  // clang-format on
-}
-
-TEST(OptionalTest, TestEqualityWithObject) {
-  auto log = Logger::Setup();
-  {
-    Logger a(17), b(42);
-    Optional<Logger> ma(a), me;
-    // Using operator== and operator!= explicitly instead of EXPECT_EQ/EXPECT_NE
-    // macros because those operators are under test.
-    log->push_back("---");
-
-    EXPECT_TRUE(ma == a);
-    EXPECT_TRUE(a == ma);
-    EXPECT_FALSE(ma == b);
-    EXPECT_FALSE(b == ma);
-    EXPECT_FALSE(me == a);
-    EXPECT_FALSE(a == me);
-
-    EXPECT_FALSE(ma != a);
-    EXPECT_FALSE(a != ma);
-    EXPECT_TRUE(ma != b);
-    EXPECT_TRUE(b != ma);
-    EXPECT_TRUE(me != a);
-    EXPECT_TRUE(a != me);
-
-    log->push_back("---");
-  }
-  // clang-format off
-  EXPECT_EQ(V("0:17. explicit constructor",
-              "1:42. explicit constructor",
-              "2:17. copy constructor (from 0:17)",
-              "---",
-              "operator== 2:17, 0:17",
-              "operator== 0:17, 2:17",
-              "operator== 2:17, 1:42",
-              "operator== 1:42, 2:17",
-              // No operator should be called when comparing to empty.
-              "operator!= 2:17, 0:17",
-              "operator!= 0:17, 2:17",
-              "operator!= 2:17, 1:42",
-              "operator!= 1:42, 2:17",
-              // No operator should be called when comparing to empty.
-              "---",
-              "2:17. destructor",
-              "1:42. destructor",
-              "0:17. destructor"),
-            *log);
-  // clang-format on
-}
-
-TEST(OptionalTest, TestSwap) {
-  auto log = Logger::Setup();
-  {
-    Logger a(17), b(42);
-    Optional<Logger> x1(a), x2(b), y1(a), y2, z1, z2;
-    log->push_back("---");
-    swap(x1, x2);  // Swap full <-> full.
-    swap(y1, y2);  // Swap full <-> empty.
-    swap(z1, z2);  // Swap empty <-> empty.
-    log->push_back("---");
-  }
-  EXPECT_EQ(V("0:17. explicit constructor", "1:42. explicit constructor",
-              "2:17. copy constructor (from 0:17)",
-              "3:42. copy constructor (from 1:42)",
-              "4:17. copy constructor (from 0:17)", "---", "swap 2:42, 3:17",
-              "5:17. move constructor (from 4:17)", "4:17. destructor", "---",
-              "5:17. destructor", "3:17. destructor", "2:42. destructor",
-              "1:42. destructor", "0:17. destructor"),
-            *log);
-}
-
-TEST(OptionalTest, TestMoveValue) {
-  auto log = Logger::Setup();
-  {
-    Optional<Logger> x(Logger(42));
-    log->push_back("---");
-    Logger moved = std::move(x.value());
-    log->push_back("---");
-  }
-  EXPECT_EQ(
-      V("0:42. explicit constructor", "1:42. move constructor (from 0:42)",
-        "0:42. destructor", "---", "2:42. move constructor (from 1:42)", "---",
-        "2:42. destructor", "1:42. destructor"),
-      *log);
-}
-
-// Nice printing available only when GTEST aware ABSL is present
-#ifdef GTEST_HAS_ABSL
-#define MaybeTestPrintTo TestPrintTo
-#define MaybeTestUnprintablePrintTo TestUnprintablePrintTo
-#else
-#define MaybeTestPrintTo DISABLED_TestPrintTo
-#define MaybeTestUnprintablePrintTo DISABLED_TestUnprintablePrintTo
-#endif
-TEST(OptionalTest, MaybeTestPrintTo) {
-  constexpr char kEmptyOptionalMessage[] = "(nullopt)";
-  const Optional<MyUnprintableType> empty_unprintable;
-  const Optional<MyPrintableType> empty_printable;
-  const Optional<MyOstreamPrintableType> empty_ostream_printable;
-  EXPECT_EQ(kEmptyOptionalMessage, ::testing::PrintToString(empty_unprintable));
-  EXPECT_EQ(kEmptyOptionalMessage, ::testing::PrintToString(empty_printable));
-  EXPECT_EQ(kEmptyOptionalMessage,
-            ::testing::PrintToString(empty_ostream_printable));
-  EXPECT_NE("(1)", ::testing::PrintToString(Optional<MyUnprintableType>({1})));
-  EXPECT_NE("(1)", ::testing::PrintToString(Optional<MyPrintableType>({1})));
-  EXPECT_EQ("(The value is 1)",
-            ::testing::PrintToString(Optional<MyPrintableType>({1})));
-  EXPECT_EQ("(1)",
-            ::testing::PrintToString(Optional<MyOstreamPrintableType>({1})));
-}
-
-TEST(OptionalTest, MaybeTestUnprintablePrintTo) {
-  struct UnprintableType {
-    uint8_t value[5];
-  };
-  Optional<UnprintableType> opt({0xa1, 0xb2, 0xc3, 0xd4, 0xe5});
-  EXPECT_EQ("(5-byte object <A1-B2 C3-D4 E5>)", ::testing::PrintToString(opt));
-}
-
-void UnusedFunctionWorkaround() {
-  // These are here to ensure we don't get warnings about ostream and PrintTo
-  // for MyPrintableType never getting called.
-  const MyPrintableType dont_warn{17};
-  const MyOstreamPrintableType dont_warn2{18};
-  std::stringstream sstr;
-  sstr << dont_warn;
-  PrintTo(dont_warn, &sstr);
-  sstr << dont_warn2;
-}
-
-}  // namespace rtc
diff --git a/api/test/simulated_network.h b/api/test/simulated_network.h
index 0006be2bc2..4ddc4377d1 100644
--- a/api/test/simulated_network.h
+++ b/api/test/simulated_network.h
@@ -17,7 +17,7 @@
 #include <queue>
 #include <vector>
 
-#include "api/optional.h"
+#include "absl/types/optional.h"
 #include "rtc_base/criticalsection.h"
 #include "rtc_base/random.h"
 #include "rtc_base/thread_annotations.h"
diff --git a/common_types.h b/common_types.h
index 4a76050963..919a947962 100644
--- a/common_types.h
+++ b/common_types.h
@@ -17,7 +17,6 @@
 #include <vector>
 
 #include "api/array_view.h"
-#include "api/optional.h"
 // TODO(sprang): Remove this include when all usage includes it directly.
 #include "api/video/video_bitrate_allocation.h"
 #include "rtc_base/checks.h"
diff --git a/media/base/vp9_profile.cc b/media/base/vp9_profile.cc
index 3ced430e5f..a28a912762 100644
--- a/media/base/vp9_profile.cc
+++ b/media/base/vp9_profile.cc
@@ -54,8 +54,8 @@ absl::optional<VP9Profile> ParseSdpForVP9Profile(
 
 bool IsSameVP9Profile(const SdpVideoFormat::Parameters& params1,
                       const SdpVideoFormat::Parameters& params2) {
-  const rtc::Optional<VP9Profile> profile = ParseSdpForVP9Profile(params1);
-  const rtc::Optional<VP9Profile> other_profile =
+  const absl::optional<VP9Profile> profile = ParseSdpForVP9Profile(params1);
+  const absl::optional<VP9Profile> other_profile =
       ParseSdpForVP9Profile(params2);
   return profile && other_profile && profile == other_profile;
 }
diff --git a/modules/audio_coding/neteq/tools/neteq_input.cc b/modules/audio_coding/neteq/tools/neteq_input.cc
index 12a75fcf41..fed3eccea7 100644
--- a/modules/audio_coding/neteq/tools/neteq_input.cc
+++ b/modules/audio_coding/neteq/tools/neteq_input.cc
@@ -34,12 +34,12 @@ TimeLimitedNetEqInput::TimeLimitedNetEqInput(std::unique_ptr<NetEqInput> input,
       start_time_ms_(input_->NextEventTime()),
       duration_ms_(duration_ms) {}
 
-rtc::Optional<int64_t> TimeLimitedNetEqInput::NextPacketTime() const {
-  return ended_ ? rtc::Optional<int64_t>() : input_->NextPacketTime();
+absl::optional<int64_t> TimeLimitedNetEqInput::NextPacketTime() const {
+  return ended_ ? absl::nullopt : input_->NextPacketTime();
 }
 
-rtc::Optional<int64_t> TimeLimitedNetEqInput::NextOutputEventTime() const {
-  return ended_ ? rtc::Optional<int64_t>() : input_->NextOutputEventTime();
+absl::optional<int64_t> TimeLimitedNetEqInput::NextOutputEventTime() const {
+  return ended_ ? absl::nullopt : input_->NextOutputEventTime();
 }
 
 std::unique_ptr<NetEqInput::PacketData> TimeLimitedNetEqInput::PopPacket() {
@@ -62,8 +62,8 @@ bool TimeLimitedNetEqInput::ended() const {
   return ended_ || input_->ended();
 }
 
-rtc::Optional<RTPHeader> TimeLimitedNetEqInput::NextHeader() const {
-  return ended_ ? rtc::Optional<RTPHeader>() : input_->NextHeader();
+absl::optional<RTPHeader> TimeLimitedNetEqInput::NextHeader() const {
+  return ended_ ? absl::nullopt : input_->NextHeader();
 }
 
 void TimeLimitedNetEqInput::MaybeSetEnded() {
diff --git a/modules/audio_coding/neteq/tools/neteq_input.h b/modules/audio_coding/neteq/tools/neteq_input.h
index a13a86eb97..16915853d1 100644
--- a/modules/audio_coding/neteq/tools/neteq_input.h
+++ b/modules/audio_coding/neteq/tools/neteq_input.h
@@ -84,18 +84,18 @@ class NetEqInput {
 class TimeLimitedNetEqInput : public NetEqInput {
  public:
   TimeLimitedNetEqInput(std::unique_ptr<NetEqInput> input, int64_t duration_ms);
-  rtc::Optional<int64_t> NextPacketTime() const override;
-  rtc::Optional<int64_t> NextOutputEventTime() const override;
+  absl::optional<int64_t> NextPacketTime() const override;
+  absl::optional<int64_t> NextOutputEventTime() const override;
   std::unique_ptr<PacketData> PopPacket() override;
   void AdvanceOutputEvent() override;
   bool ended() const override;
-  rtc::Optional<RTPHeader> NextHeader() const override;
+  absl::optional<RTPHeader> NextHeader() const override;
 
  private:
   void MaybeSetEnded();
 
   std::unique_ptr<NetEqInput> input_;
-  const rtc::Optional<int64_t> start_time_ms_;
+  const absl::optional<int64_t> start_time_ms_;
   const int64_t duration_ms_;
   bool ended_ = false;
 };
diff --git a/pc/test/framegeneratorcapturervideotracksource.h b/pc/test/framegeneratorcapturervideotracksource.h
index b406e3bfba..77e78e0c98 100644
--- a/pc/test/framegeneratorcapturervideotracksource.h
+++ b/pc/test/framegeneratorcapturervideotracksource.h
@@ -42,8 +42,8 @@ class FrameGeneratorCapturerVideoTrackSource : public VideoTrackSource {
   FrameGeneratorCapturerVideoTrackSource(Config config, Clock* clock)
       : VideoTrackSource(false /* remote */) {
     video_capturer_.reset(test::FrameGeneratorCapturer::Create(
-        config.width, config.height, rtc::nullopt, config.num_squares_generated,
-        config.frames_per_second, clock));
+        config.width, config.height, absl::nullopt,
+        config.num_squares_generated, config.frames_per_second, clock));
   }
 
   ~FrameGeneratorCapturerVideoTrackSource() = default;