diff --git a/VisualEditor.i18n.php b/VisualEditor.i18n.php
index cc5b997b32..9aff1e8598 100644
--- a/VisualEditor.i18n.php
+++ b/VisualEditor.i18n.php
@@ -34,6 +34,7 @@ $messages['en'] = array(
 	'visualeditor-annotationbutton-link-tooltip' => 'Link',
 	'visualeditor-annotationbutton-language-tooltip' => 'Language',
 	'visualeditor-annotationbutton-strikethrough-tooltip' => 'Strikethrough',
+	'visualeditor-annotationbutton-underline-tooltip' => 'Underline',
 	'visualeditor-beta-label' => 'beta',
 	'visualeditor-beta-warning' => 'VisualEditor is in \'beta\'. You may encounter software issues, and you may not be able to edit parts of the page. Click "{{int:visualeditor-ca-editsource}}" to switch to wikitext mode – unsaved changes will be lost.',
 	'visualeditor-beta-appendix' => 'beta',
@@ -253,6 +254,8 @@ See also:
 {{Identical|Language}}',
 	'visualeditor-annotationbutton-strikethrough-tooltip' => 'Tooltip text for strikethrough button.
 {{Identical|Strikethrough}}',
+	'visualeditor-annotationbutton-underline-tooltip' => 'Tooltip text for underline button.
+{{Identical|Underline}}',
 	'visualeditor-beta-label' => 'Text of tool in the toolbar that highlights that VisualEditor is still in beta.
 {{Identical|Beta}}',
 	'visualeditor-beta-warning' => "Note shown when user clicks on 'beta' label in VisualEditor, warning users that the software may have issues",
diff --git a/VisualEditor.php b/VisualEditor.php
index aac37b5ad9..1d523fd3b8 100644
--- a/VisualEditor.php
+++ b/VisualEditor.php
@@ -724,6 +724,7 @@ $wgResourceModules += array(
 			've/ui/widgets/ve.ui.LanguageInputWidget.js',
 			've/ui/tools/buttons/ve.ui.CodeButtonTool.js',
 			've/ui/tools/buttons/ve.ui.StrikethroughButtonTool.js',
+			've/ui/tools/buttons/ve.ui.UnderlineButtonTool.js',
 		),
 		'dependencies' => array(
 			'ext.visualEditor.core',
@@ -736,6 +737,7 @@ $wgResourceModules += array(
 			'visualeditor-mwmathinspector-title',
 			'visualeditor-annotationbutton-language-tooltip',
 			'visualeditor-annotationbutton-strikethrough-tooltip',
+			'visualeditor-annotationbutton-underline-tooltip',
 		),
 	),
 
diff --git a/modules/ve-mw/init/targets/ve.init.mw.ViewPageTarget.js b/modules/ve-mw/init/targets/ve.init.mw.ViewPageTarget.js
index 5634c2c187..141f1fd713 100644
--- a/modules/ve-mw/init/targets/ve.init.mw.ViewPageTarget.js
+++ b/modules/ve-mw/init/targets/ve.init.mw.ViewPageTarget.js
@@ -164,7 +164,7 @@ ve.init.mw.ViewPageTarget.compatibility = {
 ve.init.mw.ViewPageTarget.static.toolbarTools = [
 	{ 'items': [ 'undo', 'redo' ] },
 	{ 'items': [ 'mwFormat' ] },
-	{ 'items': [ 'bold', 'italic', 'mwLink', 'language', 'code', 'strikethrough', 'clear' ] },
+	{ 'items': [ 'bold', 'italic', 'strikethrough', 'underline', 'mwLink', 'language', 'code', 'clear' ] },
 	{ 'items': [ 'number', 'bullet', 'outdent', 'indent' ] },
 	{ 'items': [ 'mwMediaInsert', 'mwReference', 'mwReferenceList', 'mwTransclusion', 'mwMath', 'mwHiero' ] }
 ];
diff --git a/modules/ve/init/ve.init.Target.js b/modules/ve/init/ve.init.Target.js
index 28c246df2d..7cc8a8445b 100644
--- a/modules/ve/init/ve.init.Target.js
+++ b/modules/ve/init/ve.init.Target.js
@@ -32,7 +32,7 @@ ve.mixinClass( ve.init.Target, ve.EventEmitter );
 ve.init.Target.static.toolbarTools = [
 	{ 'items': ['undo', 'redo'] },
 	{ 'items': ['format'] },
-	{ 'items': ['bold', 'italic', 'link', 'code', 'language', 'strikethrough', 'clear'] },
+	{ 'items': ['bold', 'italic', 'link', 'code', 'language', 'underline', 'strikethrough', 'clear'] },
 	{ 'items': ['number', 'bullet', 'outdent', 'indent'] }
 ];
 
@@ -43,6 +43,7 @@ ve.init.Target.static.surfaceCommands = [
 	//'language',
 	'undo',
 	'redo',
+	//'underline',
 	//'strikethrough',
 	'indent',
 	'outdent'
diff --git a/modules/ve/ui/tools/buttons/ve.ui.UnderlineButtonTool.js b/modules/ve/ui/tools/buttons/ve.ui.UnderlineButtonTool.js
new file mode 100644
index 0000000000..ea0a5456fb
--- /dev/null
+++ b/modules/ve/ui/tools/buttons/ve.ui.UnderlineButtonTool.js
@@ -0,0 +1,43 @@
+/*!
+ * VisualEditor UserInterface UnderlineButtonTool class.
+ *
+ * @copyright 2011-2013 VisualEditor Team and others; see AUTHORS.txt
+ * @license The MIT License (MIT); see LICENSE.txt
+ */
+
+/**
+ * UserInterface underline button tool.
+ *
+ * @class
+ * @extends ve.ui.AnnotationButtonTool
+ * @constructor
+ * @param {ve.ui.SurfaceToolbar} toolbar
+ * @param {Object} [config] Config options
+ */
+ve.ui.UnderlineButtonTool = function VeUiUnderlineButtonTool( toolbar, config ) {
+	// Parent constructor
+	ve.ui.AnnotationButtonTool.call( this, toolbar, config );
+};
+
+/* Inheritance */
+
+ve.inheritClass( ve.ui.UnderlineButtonTool, ve.ui.AnnotationButtonTool );
+
+/* Static Properties */
+
+ve.ui.UnderlineButtonTool.static.name = 'underline';
+
+ve.ui.UnderlineButtonTool.static.icon = {
+	'default': 'underline-a',
+	'en': 'underline-u'
+};
+
+ve.ui.UnderlineButtonTool.static.titleMessage = 'visualeditor-annotationbutton-underline-tooltip';
+
+ve.ui.UnderlineButtonTool.static.annotation = { 'name': 'textStyle/underline' };
+
+/* Registration */
+
+ve.ui.toolFactory.register( 'underline', ve.ui.UnderlineButtonTool );
+
+ve.ui.commandRegistry.register( 'underline', 'annotation', 'toggle', 'textStyle/underline' );