diff --git a/activesupport/CHANGELOG b/activesupport/CHANGELOG
index be7eba5b0c58ad4dc996948850ebab057da4baac..fe243d4abf1fb1a042d5c6650b27c1164a2652a0 100644
--- a/activesupport/CHANGELOG
+++ b/activesupport/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Added Hash#except which is the inverse of Hash#slice -- return the hash except the keys that are specified [DHH]
+
 * Added support for pluralization with a different starting letter than the singular version (cow/kine) #4929 [norri_b/hasmanyjosh]
 
 * Demote Hash#to_xml to use XmlSimple#xml_in_string so it can't read files or stdin.  #8453 [candlerb, Jeremy Kemper]
diff --git a/activesupport/lib/active_support/core_ext/hash.rb b/activesupport/lib/active_support/core_ext/hash.rb
index 2a99468b4e9ecad51ac734cd938e33fdf1b2496f..b805d2da62220994e3f98bf62a022ccf4e692f2c 100644
--- a/activesupport/lib/active_support/core_ext/hash.rb
+++ b/activesupport/lib/active_support/core_ext/hash.rb
@@ -1,4 +1,4 @@
-%w(keys indifferent_access reverse_merge conversions diff slice).each do |ext|
+%w(keys indifferent_access reverse_merge conversions diff slice except).each do |ext|
   require "#{File.dirname(__FILE__)}/hash/#{ext}"
 end
 
@@ -9,4 +9,5 @@ class Hash #:nodoc:
   include ActiveSupport::CoreExtensions::Hash::Conversions
   include ActiveSupport::CoreExtensions::Hash::Diff
   include ActiveSupport::CoreExtensions::Hash::Slice
+  include ActiveSupport::CoreExtensions::Hash::Except
 end
diff --git a/activesupport/lib/active_support/core_ext/hash/except.rb b/activesupport/lib/active_support/core_ext/hash/except.rb
new file mode 100644
index 0000000000000000000000000000000000000000..8362cd880e4fc505c3067be2758464c83b2029a4
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/hash/except.rb
@@ -0,0 +1,24 @@
+require 'set'
+
+module ActiveSupport #:nodoc:
+  module CoreExtensions #:nodoc:
+    module Hash #:nodoc:
+      # Return a hash that includes everything but the given keys. This is useful for
+      # limiting a set of parameters to everything but a few known toggles:
+      #
+      #   @person.update_attributes(params[:person].except(:admin))
+      module Except
+        # Returns a new hash without the given keys.
+        def except(*keys)
+          rejected = Set.new(respond_to?(:convert_key) ? keys.map { |key| convert_key(key) } : keys)
+          reject { |key,| rejected.include?(key) }
+        end
+
+        # Replaces the hash without only the given keys.
+        def except!(*keys)
+          replace(except(*keys))
+        end
+      end
+    end
+  end
+end
diff --git a/activesupport/test/core_ext/hash_ext_test.rb b/activesupport/test/core_ext/hash_ext_test.rb
index cae19a9335e707fbd59a85bf64fa0d1b72f62254..c2b7a7f1eb6102a282d9ec1e996bc96fc02d5308 100644
--- a/activesupport/test/core_ext/hash_ext_test.rb
+++ b/activesupport/test/core_ext/hash_ext_test.rb
@@ -277,6 +277,19 @@ def test_indifferent_slice
       assert_equal expected, copy
     end
   end
+
+  def test_except
+    original = { :a => 'x', :b => 'y', :c => 10 }
+    expected = { :a => 'x', :b => 'y' }
+
+    # Should return a new hash with only the given keys.
+    assert_equal expected, original.except(:c)
+    assert_not_equal expected, original
+
+    # Should replace the hash with only the given keys.
+    assert_equal expected, original.except!(:c)
+    assert_equal expected, original
+  end
 end
 
 class IWriteMyOwnXML