diff --git a/app/models/user.rb b/app/models/user.rb
index fdce215e4f0..4509e236147 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -93,9 +93,15 @@ class User < ActiveRecord::Base
     ALWAYS = -1
     LAST_VISIT = -2
   end
+  
+  GLOBAL_USERNAME_LENGTH_RANGE = 3..15
 
   def self.username_length
-    3..15
+    if SiteSetting.enforce_global_nicknames
+      GLOBAL_USERNAME_LENGTH_RANGE
+    else
+      SiteSetting.min_username_length.to_i..GLOBAL_USERNAME_LENGTH_RANGE.end
+    end
   end
 
   def custom_groups
diff --git a/config/locales/server.en.yml b/config/locales/server.en.yml
index 8e1159ed27c..eddaba38d18 100644
--- a/config/locales/server.en.yml
+++ b/config/locales/server.en.yml
@@ -672,7 +672,9 @@ en:
     invite_only: "Public registration is disabled, new users must be invited"
 
     login_required: "Require authentication to read posts"
-
+    
+    min_username_length: "Minimum username length. (Does not apply if global nickname uniqueness is forced)"
+    
     min_password_length: "Minimum password length."
     block_common_passwords: "Don't allow passwords that are in the 5000 most common passwords."
 
diff --git a/config/site_settings.yml b/config/site_settings.yml
index e740fdf862d..74cdf3d04c2 100644
--- a/config/site_settings.yml
+++ b/config/site_settings.yml
@@ -93,6 +93,9 @@ users:
   must_approve_users:
     client: true
     default: false
+  min_username_length:
+    client: true
+    default: 3
   min_password_length:
     client: true
     default: 8
diff --git a/spec/models/user_spec.rb b/spec/models/user_spec.rb
index 656a8791d9a..e24ca1a1c2c 100644
--- a/spec/models/user_spec.rb
+++ b/spec/models/user_spec.rb
@@ -174,7 +174,35 @@ describe User do
         myself.reload.username.should == 'HanSolo'
       end
     end
-
+    
+    describe 'allow custom minimum username length from site settings' do
+      before do
+        @custom_min = User::GLOBAL_USERNAME_LENGTH_RANGE.begin - 1
+        SiteSetting.stubs("min_username_length").returns(@custom_min)
+      end
+      
+      it 'should allow a shorter username than default' do
+        result = user.change_username('a' * @custom_min)
+        result.should_not be_false
+      end
+      
+      it 'should not allow a shorter username than limit' do
+        result = user.change_username('a' * (@custom_min - 1))
+        result.should be_false
+      end   
+      
+      it 'should not allow a longer username than limit' do
+        result = user.change_username('a' * (User::GLOBAL_USERNAME_LENGTH_RANGE.end + 1))
+        result.should be_false        
+      end
+      
+      it 'should use default length for validation if enforce_global_nicknames is true' do
+        SiteSetting.stubs('enforce_global_nicknames').returns(true)
+        
+        User::username_length.begin.should == User::GLOBAL_USERNAME_LENGTH_RANGE.begin
+        User::username_length.end.should == User::GLOBAL_USERNAME_LENGTH_RANGE.end 
+      end
+    end
   end
 
   describe 'delete posts' do
@@ -422,7 +450,7 @@ describe User do
   end
 
   describe 'username format' do
-    it "should always be 3 chars or longer" do
+    it "should be #{SiteSetting.min_username_length} chars or longer" do
       @user = Fabricate.build(:user)
       @user.username = 'ss'
       @user.save.should == false