diff --git a/doc/maintainers.rdoc b/doc/maintainers.rdoc
index dbb4fd2ca3..cde67e9bc1 100644
--- a/doc/maintainers.rdoc
+++ b/doc/maintainers.rdoc
@@ -105,8 +105,6 @@ Zachary Scott (zzak)
   Tanaka Akira (akr)
 [lib/shellwords.rb]
   Akinori MUSHA (knu)
-[lib/singleton.rb]
-  Yukihiro Matsumoto (matz)
 [lib/tempfile.rb]
   _unmaintained_
 [lib/tmpdir.rb]
@@ -220,6 +218,9 @@ Zachary Scott (zzak)
 [lib/rss.rb, lib/rss/*]
   Kouhei Sutou (kou)
   https://github.com/ruby/rss
+[lib/singleton.rb]
+  Yukihiro Matsumoto (matz)
+  https://github.com/ruby/singleton
 [lib/thwait.rb]
   Keiju ISHITSUKA (keiju)
   https://github.com/ruby/thwait
diff --git a/doc/standard_library.rdoc b/doc/standard_library.rdoc
index 975bc39f94..7517c3e288 100644
--- a/doc/standard_library.rdoc
+++ b/doc/standard_library.rdoc
@@ -41,7 +41,6 @@ Gem:: Package management framework for Ruby
 SecureRandom:: Interface for secure random number generator
 Set:: Provides a class to deal with collections of unordered, unique values
 Shellwords:: Manipulates strings with word parsing rules of UNIX Bourne shell
-Singleton:: Implementation of the Singleton pattern for Ruby
 Tempfile:: A utility class for managing temporary files
 Time:: Extends the Time class with methods for parsing and conversion
 Timeout:: Auto-terminate potentially long-running operations in Ruby
@@ -87,6 +86,7 @@ Racc:: A LALR(1) parser generator written in Ruby.
 RDoc:: Produces HTML and command-line documentation for Ruby
 REXML:: An XML toolkit for Ruby
 RSS:: Family of libraries that support various formats of XML "feeds"
+Singleton:: Implementation of the Singleton pattern for Ruby
 Tracer:: Outputs a source level execution trace of a Ruby program
 WEBrick:: An HTTP server toolkit for Ruby
 
diff --git a/lib/singleton/singleton.gemspec b/lib/singleton/singleton.gemspec
new file mode 100644
index 0000000000..f7ee6bb2dc
--- /dev/null
+++ b/lib/singleton/singleton.gemspec
@@ -0,0 +1,27 @@
+begin
+  require_relative "lib/singleton/version"
+rescue LoadError # Fallback to load version file in ruby core repository
+  require_relative "version"
+end
+
+Gem::Specification.new do |spec|
+  spec.name          = "singleton"
+  spec.version       = Singleton::VERSION
+  spec.authors       = ["Yukihiro Matsumoto"]
+  spec.email         = ["matz@ruby-lang.org"]
+
+  spec.summary       = %q{The Singleton module implements the Singleton pattern.}
+  spec.description   = spec.summary
+  spec.homepage      = "https://github.com/ruby/singleton"
+  spec.license       = "BSD-2-Clause"
+
+  spec.metadata["homepage_uri"] = spec.homepage
+  spec.metadata["source_code_uri"] = spec.homepage
+
+  spec.files         = Dir.chdir(File.expand_path('..', __FILE__)) do
+    `git ls-files -z`.split("\x0").reject { |f| f.match(%r{^(test|spec|features)/}) }
+  end
+  spec.bindir        = "exe"
+  spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
+  spec.require_paths = ["lib"]
+end
diff --git a/lib/singleton/version.rb b/lib/singleton/version.rb
new file mode 100644
index 0000000000..01ab1eb5fa
--- /dev/null
+++ b/lib/singleton/version.rb
@@ -0,0 +1,3 @@
+module Singleton
+  VERSION = "0.1.0"
+end
diff --git a/tool/sync_default_gems.rb b/tool/sync_default_gems.rb
index 0d9defe278..eee06f001f 100644
--- a/tool/sync_default_gems.rb
+++ b/tool/sync_default_gems.rb
@@ -33,6 +33,7 @@
 # * https://github.com/ruby/e2mmap
 # * https://github.com/ruby/mutex_m
 # * https://github.com/ruby/racc
+# * https://github.com/ruby/singleton
 #
 
 require 'fileutils'
@@ -72,7 +73,8 @@ $repositories = {
   forwardable: "ruby/forwardable",
   e2mmap: "ruby/e2mmap",
   mutex_m: "ruby/mutex_m",
-  racc: "ruby/racc"
+  racc: "ruby/racc",
+  singleton: "ruby/singleton"
 }
 
 def sync_default_gems(gem)
@@ -210,7 +212,7 @@ def sync_default_gems(gem)
     rm_rf("test/racc/lib")
     rm_rf("lib/racc/cparse-jruby.jar")
     `git checkout ext/racc/cparse/README ext/racc/cparse/depend`
-  when "rexml", "rss", "matrix", "irb", "csv", "logger", "ostruct", "webrick", "fileutils", "forwardable", "prime", "tracer", "ipaddr", "mutex_m"
+  when "rexml", "rss", "matrix", "irb", "csv", "logger", "ostruct", "webrick", "fileutils", "forwardable", "prime", "tracer", "ipaddr", "mutex_m", "singleton"
     sync_lib gem
   else
   end