diff --git a/doc/maintainers.rdoc b/doc/maintainers.rdoc
index f0d564da01..8b30971463 100644
--- a/doc/maintainers.rdoc
+++ b/doc/maintainers.rdoc
@@ -64,8 +64,6 @@ Zachary Scott (zzak)
   Koichi Sasada (ko1)
 [ext/objspace]
   _unmaintained_
-[ext/pathname]
-  Tanaka Akira (akr)
 [ext/pty]
   _unmaintained_
 [ext/ripper]
@@ -334,6 +332,9 @@ Zachary Scott (zzak)
   Kazuki Yamaguchi (rhe)
   https://github.com/ruby/openssl
   https://rubygems.org/gems/openssl
+[ext/pathname]
+  Tanaka Akira (akr)
+  https://github.com/ruby/pathname
 [ext/psych]
   Aaron Patterson (tenderlove), Hiroshi SHIBATA (hsbt)
   https://github.com/ruby/psych
diff --git a/doc/standard_library.rdoc b/doc/standard_library.rdoc
index 926ec41840..7d1bff8eb4 100644
--- a/doc/standard_library.rdoc
+++ b/doc/standard_library.rdoc
@@ -20,7 +20,6 @@ Coverage:: Provides coverage measurement for Ruby
 Digest:: Provides a framework for message digest libraries
 Monitor:: Provides an object or module to use safely by more than one thread
 objspace:: Extends ObjectSpace module to add methods for internal statistics
-Pathname:: Representation of the name of a file or directory on the filesystem
 PTY:: Creates and manages pseudo terminals
 Ripper:: Provides an interface for parsing Ruby programs into S-expressions
 Socket:: Access underlying OS socket implementations
@@ -60,6 +59,7 @@ Observable:: Provides a mechanism for publish/subscribe pattern in Ruby
 Open3:: Provides access to stdin, stdout and stderr when running other programs
 OpenStruct:: Class to build custom data structures, similar to a Hash
 OpenURI:: An easy-to-use wrapper for Net::HTTP, Net::HTTPS and Net::FTP
+Pathname:: Representation of the name of a file or directory on the filesystem
 PP:: Provides a PrettyPrinter for Ruby objects
 PrettyPrinter:: Implements a pretty printing algorithm for readable structure
 Prime:: Prime numbers and factorization library
diff --git a/ext/pathname/pathname.gemspec b/ext/pathname/pathname.gemspec
new file mode 100644
index 0000000000..8593f9e9c7
--- /dev/null
+++ b/ext/pathname/pathname.gemspec
@@ -0,0 +1,25 @@
+Gem::Specification.new do |spec|
+  spec.name          = "pathname"
+  spec.version       = "0.1.0"
+  spec.authors       = ["Tanaka Akira"]
+  spec.email         = ["akr@fsij.org"]
+
+  spec.summary       = %q{Representation of the name of a file or directory on the filesystem}
+  spec.description   = %q{Representation of the name of a file or directory on the filesystem}
+  spec.homepage      = "https://github.com/ruby/pathname"
+  spec.required_ruby_version = Gem::Requirement.new(">= 2.3.0")
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
+
+  spec.metadata["homepage_uri"] = spec.homepage
+  spec.metadata["source_code_uri"] = spec.homepage
+
+  # Specify which files should be added to the gem when it is released.
+  # The `git ls-files -z` loads the files in the RubyGem that have been added into git.
+  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"]
+  spec.extensions    = %w[ext/pathname/extconf.rb]
+end
diff --git a/tool/sync_default_gems.rb b/tool/sync_default_gems.rb
index 685e5745ad..57aa347566 100644
--- a/tool/sync_default_gems.rb
+++ b/tool/sync_default_gems.rb
@@ -80,6 +80,7 @@ REPOSITORIES = {
   pp: "ruby/pp",
   prettyprint: "ruby/prettyprint",
   drb: "ruby/drb",
+  pathname: "ruby/pathname",
 }
 
 def sync_default_gems(gem)
@@ -308,6 +309,12 @@ def sync_default_gems(gem)
     cp_r("#{upstream}/test/bigdecimal", "test")
     cp_r("#{upstream}/bigdecimal.gemspec", "ext/bigdecimal")
     `git checkout ext/bigdecimal/depend`
+  when "pathname"
+    rm_rf(%w[ext/pathname test/pathname])
+    cp_r("#{upstream}/ext/pathname", "ext")
+    cp_r("#{upstream}/test/pathname", "test")
+    cp_r("#{upstream}/pathname.gemspec", "ext/pathname")
+    `git checkout ext/pathname/depend`
   else
     sync_lib gem, upstream
   end