diff --git a/lib/protobuf/generators/group_generator.rb b/lib/protobuf/generators/group_generator.rb
index 33e7b5be..a6f4241a 100644
--- a/lib/protobuf/generators/group_generator.rb
+++ b/lib/protobuf/generators/group_generator.rb
@@ -4,6 +4,7 @@
 require 'protobuf/generators/message_generator'
 require 'protobuf/generators/option_generator'
 require 'protobuf/generators/service_generator'
+require 'protobuf/generators/oneof_group_generator'
 
 module Protobuf
   module Generators
@@ -27,6 +28,12 @@ def add_options(option_descriptor)
         @groups[:options] << OptionGenerator.new(option_descriptor, indent_level)
       end
 
+      def add_oneof_groups(field_descriptors, msg_descriptor)
+        return unless msg_descriptor.oneof_decl.length > 0
+
+        @groups[:oneof_group] << OneofGroupGenerator.new(msg_descriptor.oneof_decl, field_descriptors, indent_level)
+      end
+
       def add_enums(enum_descriptors, options)
         enum_descriptors.each do |enum_descriptor|
           @groups[:enum] << EnumGenerator.new(enum_descriptor, indent_level, options)
diff --git a/lib/protobuf/generators/message_generator.rb b/lib/protobuf/generators/message_generator.rb
index bbaf84d5..c38b49d4 100644
--- a/lib/protobuf/generators/message_generator.rb
+++ b/lib/protobuf/generators/message_generator.rb
@@ -44,6 +44,9 @@ def compile_message
               group.add_messages(descriptor.nested_type, :extension_fields => @extension_fields, :namespace => type_namespace)
               group.add_comment(:options, 'Message Options')
               group.add_options(descriptor.options) if options?
+              group.add_oneof_groups(descriptor.field, descriptor)
+              group.add_comment(:oneof_group, 'Oneof Groups')
+
               group.add_message_fields(descriptor.field, descriptor)
               self.class.validate_tags(fully_qualified_type_namespace, descriptor.field.map(&:number))
 
@@ -54,7 +57,7 @@ def compile_message
 
               group.add_extension_fields(message_extension_fields)
 
-              group.order = [:message, :options, :field, :extension_range, :extension_field]
+              group.order = [:message, :options, :oneof_group, :field, :extension_range, :extension_field]
               print group.to_s
             end
           end
diff --git a/lib/protobuf/generators/oneof_group_generators.rb b/lib/protobuf/generators/oneof_group_generators.rb
new file mode 100644
index 00000000..b8ce86a5
--- /dev/null
+++ b/lib/protobuf/generators/oneof_group_generators.rb
@@ -0,0 +1,29 @@
+require 'protobuf/generators/base'
+
+module Protobuf
+  module Generators
+    class OneofGroupGenerator < Base
+      def initialize(oneof_decl, field_descriptors, indent_level, options = {})
+        super(oneof_decl, indent_level, options)
+        @field_descriptors = field_descriptors
+      end
+
+      def compile
+        run_once(:compile) do
+          descriptor.each_with_index do |oneof_descriptor, idx|
+            puts build_value(oneof_descriptor.name, idx)
+          end
+          puts
+        end
+      end
+
+      def build_value(name, oneof_index)
+        oneof_fields = @field_descriptors.select { |field_descriptor| field_descriptor.oneof_index == oneof_index }
+
+        "oneof_group :#{name.strip}, [:#{oneof_fields.map(&:name).join(', :')}]"
+      end
+    end
+  end
+end
+
+
diff --git a/lib/protobuf/message.rb b/lib/protobuf/message.rb
index a13c0d19..3f12d5be 100644
--- a/lib/protobuf/message.rb
+++ b/lib/protobuf/message.rb
@@ -1,5 +1,6 @@
 require 'protobuf/message/fields'
 require 'protobuf/message/serialization'
+require 'protobuf/message/oneof_groups'
 require 'protobuf/varint'
 
 module Protobuf
@@ -10,6 +11,7 @@ class Message
     #
 
     extend ::Protobuf::Message::Fields
+    extend ::Protobuf::Message::OneofGroups
     include ::Protobuf::Message::Serialization
     ::Protobuf::Optionable.inject(self) { ::Google::Protobuf::MessageOptions }
 
diff --git a/lib/protobuf/message/oneof_groups.rb b/lib/protobuf/message/oneof_groups.rb
new file mode 100644
index 00000000..74e3451d
--- /dev/null
+++ b/lib/protobuf/message/oneof_groups.rb
@@ -0,0 +1,31 @@
+module Protobuf
+  class Message
+    module OneofGroups
+      def self.extended(other)
+        other.extend(ClassMethods)
+      end
+
+      module ClassMethods
+        # Define a oneOf group
+        #
+        def oneof_group(group_name, field_names)
+          oneof_groups[group_name] = field_names
+        end
+
+        def get_oneof_group(group_name)
+          oneof_groups[group_name]
+        end
+
+        def raise_if_oneof_group_name_collision(group_name)
+          if get_oneof_group(group_name)
+            fail DuplicateOneofGroupNameError, %(Oneof group name #{group_name} has already been used in "#{name}".)
+          end
+        end
+
+        def oneof_groups
+          @oneof_groups ||= {}
+        end
+      end
+    end
+  end
+end