diff --git a/Gemfile b/Gemfile
index df43c352..89bf833e 100644
--- a/Gemfile
+++ b/Gemfile
@@ -24,6 +24,7 @@ gem 'rouge'
 gem 'haml'
 gem 'pandoc-ruby'        # for benefit reports in ConTeXt
 gem 'git'                # for version history and tagging info
+gem 'builder'            # for sitemap
 
 group :development, optional: true do
   gem 'guard'
diff --git a/Gemfile.lock b/Gemfile.lock
index 08c812bb..f1ec9847 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -25,7 +25,7 @@ GIT
 
 GIT
   remote: https://github.com/ruby-rdf/rdf.git
-  revision: e1ff91841066369b8917dd21be9564452a6ea18a
+  revision: 4740b4a52bf358656d01d93adc5174d5fe07aec8
   branch: develop
   specs:
     rdf (2.1.0)
@@ -40,7 +40,8 @@ GEM
       i18n (~> 0.7)
       minitest (~> 5.1)
       tzinfo (~> 1.1)
-    addressable (2.4.0)
+    addressable (2.5.0)
+      public_suffix (~> 2.0, >= 2.0.2)
     adsf (1.2.1)
       rack (>= 1.0.0)
     bcp47 (0.3.3)
@@ -191,11 +192,12 @@ GEM
     pandoc-ruby (2.0.1)
     parallel (1.9.0)
     pipe-run (0.3.0)
-    posix-spawn (0.3.11)
+    posix-spawn (0.3.12)
     pry (0.10.4)
       coderay (~> 1.1.0)
       method_source (~> 0.8.1)
       slop (~> 3.4)
+    public_suffix (2.0.4)
     pygments.rb (0.6.3)
       posix-spawn (~> 0.3.6)
       yajl-ruby (~> 1.2.0)
@@ -330,6 +332,7 @@ PLATFORMS
 DEPENDENCIES
   activesupport
   adsf
+  builder
   chunky_png
   compass
   ghi
diff --git a/lib/helpers/xml_sitemap.rb b/lib/helpers/xml_sitemap.rb
new file mode 100644
index 00000000..86809d3d
--- /dev/null
+++ b/lib/helpers/xml_sitemap.rb
@@ -0,0 +1,48 @@
+module Nanoc::Helpers
+  # @see http://nanoc.ws/doc/reference/helpers/#xmlsitemap
+  module XMLSitemap
+    include LifePreserver::LinkTo
+
+    # @option params [Array] :items
+    # @option params [Proc] :rep_select
+    #
+    # @return [String]
+    def xml_sitemap(params = {})
+      require 'builder'
+
+      # Extract parameters
+      items       = params.fetch(:items) { @items.reject { |i| i[:is_hidden] } }
+      select_proc = params.fetch(:rep_select, nil)
+
+      # Create builder
+      buffer = ''
+      xml = Builder::XmlMarkup.new(target: buffer, indent: 2)
+
+      # Check for required attributes
+      if @config[:base_url].nil?
+        raise 'The Nanoc::Helpers::XMLSitemap helper requires the site configuration to specify the base URL for the site.'
+      end
+
+      # Build sitemap
+      xml.instruct!
+      xml.urlset(xmlns: 'http://www.sitemaps.org/schemas/sitemap/0.9') do
+        # Add item
+        items.sort_by(&:identifier).each do |item|
+          reps = item.reps.reject { |r| r.raw_path.nil? }
+          reps.reject! { |r| !select_proc[r] } if select_proc
+          reps.sort_by { |r| r.name.to_s }.each do |rep|
+            xml.url do
+              xml.loc path_to(rep, global: true)
+              xml.lastmod item[:mtime].__nanoc_to_iso8601_date unless item[:mtime].nil?
+              xml.changefreq item[:changefreq] unless item[:changefreq].nil?
+              xml.priority item[:priority] unless item[:priority].nil?
+            end
+          end
+        end
+      end
+
+      # Return sitemap
+      buffer
+    end
+  end
+end