diff --git a/lib/linguist/language.rb b/lib/linguist/language.rb
index b4c2d5f0..8f6686d1 100644
--- a/lib/linguist/language.rb
+++ b/lib/linguist/language.rb
@@ -2,22 +2,42 @@ require 'yaml'
 
 module Linguist
   class Language
-    @name_index = {}
+    @name_index      = {}
+    @extension_index = {}
 
     def self.create(attributes = {})
       language = new(attributes)
 
       @name_index[language.name.downcase] = language
 
+      language.extensions.each do |extension|
+        @extension_index[extension] = language
+        @extension_index[extension.sub(/^./, '')] = language
+      end
+
       language
     end
 
+    def self.[](name)
+      find_by_name(name)
+    end
+
     def self.find_by_name(name)
       @name_index[name.downcase]
     end
 
-    def self.[](name)
-      find_by_name(name)
+    def self.find_by_extension(filename)
+      basename = File.basename(filename)
+
+      if basename[0] == ?.
+        ext = basename
+      elsif basename.include?('.')
+        ext = File.extname(basename)
+      else
+        ext = basename
+      end
+
+      @extension_index[ext]
     end
 
     attr_reader :name, :extensions
diff --git a/test/test_language.rb b/test/test_language.rb
index b3010e43..1ad96405 100644
--- a/test/test_language.rb
+++ b/test/test_language.rb
@@ -6,9 +6,24 @@ class TestLanguage < Test::Unit::TestCase
   include Linguist
 
   def test_find_by_name
-    assert_equal "Ruby", Language.find_by_name('Ruby').name
-    assert_equal "Ruby", Language.find_by_name('ruby').name
-    assert_equal "Ruby", Language.find_by_name('RUBY').name
+    ruby = Language['Ruby']
+    assert_equal ruby, Language.find_by_name('Ruby')
+    assert_equal ruby, Language.find_by_name('ruby')
+    assert_equal ruby, Language.find_by_name('RUBY')
+  end
+
+  def test_find_by_extension
+    ruby = Language['Ruby']
+    assert_equal ruby, Language.find_by_extension('.rb')
+    assert_equal ruby, Language.find_by_extension('rb')
+    assert_equal ruby, Language.find_by_extension('foo.rb')
+    assert_equal ruby, Language.find_by_extension('./foo.rb')
+    assert_equal ruby, Language.find_by_extension('foo/bar.rb')
+
+    # TODO: Review questionable usage
+    assert_equal ruby, Language.find_by_extension('Rakefile')
+    assert_equal ruby, Language.find_by_extension('vendor/Rakefile')
+    assert_equal ruby, Language.find_by_extension('./Rakefile')
   end
 
   def test_name