diff --git a/lib/googleauth/user_refresh.rb b/lib/googleauth/user_refresh.rb
new file mode 100644
index 0000000..3cfb1db
--- /dev/null
+++ b/lib/googleauth/user_refresh.rb
@@ -0,0 +1,76 @@
+# Copyright 2015, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+require 'googleauth/signet'
+require 'googleauth/credentials_loader'
+require 'multi_json'
+
+module Google
+  # Module Auth provides classes that provide Google-specific authorization
+  # used to access Google APIs.
+  module Auth
+    # Authenticates requests using User Refresh credentials.
+    #
+    # This class allows authorizing requests from user refresh tokens.
+    #
+    # This the end of the result of a 3LO flow.  E.g, the end result of
+    # 'gcloud auth login' saves a file with these contents in well known
+    # location
+    #
+    # cf [Application Default Credentials](http://goo.gl/mkAHpZ)
+    class UserRefreshCredentials < Signet::OAuth2::Client
+      TOKEN_CRED_URI = 'https://www.googleapis.com/oauth2/v3/token'
+      extend CredentialsLoader
+
+      # Reads the client_id, client_secret and refresh_token fields from the
+      # JSON key.
+      def self.read_json_key(json_key_io)
+        json_key = MultiJson.load(json_key_io.read)
+        wanted = %w(client_id client_secret refresh_token)
+        wanted.each do |key|
+          fail "the json is missing the #{key} field" unless json_key.key?(key)
+        end
+        json_key
+      end
+
+      # Initializes a UserRefreshCredentials.
+      #
+      # @param scope [string|array] the scope(s) to access
+      # @param json_key_io [IO] an IO from which the JSON key can be read
+      def initialize(scope, json_key_io)
+        user_creds = self.class.read_json_key(json_key_io)
+        super(token_credential_uri: TOKEN_CRED_URI,
+              client_id: user_creds['client_id'],
+              client_secret: user_creds['client_secret'],
+              refresh_token: user_creds['refresh_token'],
+              scope: scope)
+      end
+    end
+  end
+end
diff --git a/spec/googleauth/user_refresh_spec.rb b/spec/googleauth/user_refresh_spec.rb
new file mode 100644
index 0000000..bbf23d2
--- /dev/null
+++ b/spec/googleauth/user_refresh_spec.rb
@@ -0,0 +1,170 @@
+# Copyright 2015, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+spec_dir = File.expand_path(File.join(File.dirname(__FILE__)))
+$LOAD_PATH.unshift(spec_dir)
+$LOAD_PATH.uniq!
+
+require 'apply_auth_examples'
+require 'fileutils'
+require 'googleauth/user_refresh'
+require 'jwt'
+require 'multi_json'
+require 'openssl'
+require 'spec_helper'
+require 'tmpdir'
+
+describe Google::Auth::UserRefreshCredentials do
+  UserRefreshCredentials = Google::Auth::UserRefreshCredentials
+  CredentialsLoader = Google::Auth::CredentialsLoader
+
+  before(:example) do
+    @key = OpenSSL::PKey::RSA.new(2048)
+    @client = UserRefreshCredentials.new(
+        'https://www.googleapis.com/auth/userinfo.profile',
+        StringIO.new(cred_json_text))
+  end
+
+  def make_auth_stubs(opts = {})
+    access_token = opts[:access_token] || ''
+    Faraday::Adapter::Test::Stubs.new do |stub|
+      stub.post('/oauth2/v3/token') do |env|
+        params = Addressable::URI.form_unencode(env[:body])
+        want = %w(grant_type refresh_token)
+        expect(params.assoc('grant_type')).to eq(want)
+        build_access_token_json(access_token)
+      end
+    end
+  end
+
+  def cred_json_text(missing = nil)
+    cred_json = {
+      client_secret: 'privatekey',
+      client_id: 'client123',
+      refresh_token: 'refreshtoken',
+      type: 'authorized_user'
+    }
+    cred_json.delete(missing.to_sym) unless missing.nil?
+    MultiJson.dump(cred_json)
+  end
+
+  it_behaves_like 'apply/apply! are OK'
+
+  describe '#from_env' do
+    before(:example) do
+      @var_name = CredentialsLoader::ENV_VAR
+      @orig = ENV[@var_name]
+      @scope = 'https://www.googleapis.com/auth/userinfo.profile'
+      @clz = UserRefreshCredentials
+    end
+
+    after(:example) do
+      ENV[@var_name] = @orig unless @orig.nil?
+    end
+
+    it 'returns nil if the GOOGLE_APPLICATION_CREDENTIALS is unset' do
+      ENV.delete(@var_name) unless ENV[@var_name].nil?
+      expect(UserRefreshCredentials.from_env(@scope)).to be_nil
+    end
+
+    it 'fails if the GOOGLE_APPLICATION_CREDENTIALS path does not exist' do
+      ENV.delete(@var_name) unless ENV[@var_name].nil?
+      expect(UserRefreshCredentials.from_env(@scope)).to be_nil
+      Dir.mktmpdir do |dir|
+        key_path = File.join(dir, 'does-not-exist')
+        ENV[@var_name] = key_path
+        expect { @clz.from_env(@scope) }.to raise_error
+      end
+    end
+
+    it 'fails if the GOOGLE_APPLICATION_CREDENTIALS path file is invalid' do
+      needed = %w(client_id client_secret refresh_token)
+      needed.each do |missing|
+        Dir.mktmpdir do |dir|
+          key_path = File.join(dir, 'my_cert_file')
+          FileUtils.mkdir_p(File.dirname(key_path))
+          File.write(key_path, cred_json_text(missing))
+          ENV[@var_name] = key_path
+          expect { @clz.from_env(@scope) }.to raise_error
+        end
+      end
+    end
+
+    it 'succeeds when the GOOGLE_APPLICATION_CREDENTIALS file is valid' do
+      Dir.mktmpdir do |dir|
+        key_path = File.join(dir, 'my_cert_file')
+        FileUtils.mkdir_p(File.dirname(key_path))
+        File.write(key_path, cred_json_text)
+        ENV[@var_name] = key_path
+        expect(@clz.from_env(@scope)).to_not be_nil
+      end
+    end
+  end
+
+  describe '#from_well_known_path' do
+    before(:example) do
+      @home = ENV['HOME']
+      @scope = 'https://www.googleapis.com/auth/userinfo.profile'
+      @known_path = CredentialsLoader::WELL_KNOWN_PATH
+      @clz = UserRefreshCredentials
+    end
+
+    after(:example) do
+      ENV['HOME'] = @home unless @home == ENV['HOME']
+    end
+
+    it 'is nil if no file exists' do
+      ENV['HOME'] = File.dirname(__FILE__)
+      expect(UserRefreshCredentials.from_well_known_path(@scope)).to be_nil
+    end
+
+    it 'fails if the file is invalid' do
+      needed = %w(client_id client_secret refresh_token)
+      needed.each do |missing|
+        Dir.mktmpdir do |dir|
+          key_path = File.join(dir, '.config', @known_path)
+          FileUtils.mkdir_p(File.dirname(key_path))
+          File.write(key_path, cred_json_text(missing))
+          ENV['HOME'] = dir
+          expect { @clz.from_env(@scope) }.to raise_error
+        end
+      end
+    end
+
+    it 'successfully loads the file when it is present' do
+      Dir.mktmpdir do |dir|
+        key_path = File.join(dir, '.config', @known_path)
+        FileUtils.mkdir_p(File.dirname(key_path))
+        File.write(key_path, cred_json_text)
+        ENV['HOME'] = dir
+        expect(@clz.from_well_known_path(@scope)).to_not be_nil
+      end
+    end
+  end
+end