diff --git a/packages/notus/lib/src/document/attributes.dart b/packages/notus/lib/src/document/attributes.dart
index f2f222075..6b1b3746c 100644
--- a/packages/notus/lib/src/document/attributes.dart
+++ b/packages/notus/lib/src/document/attributes.dart
@@ -74,6 +74,7 @@ class NotusAttribute<T> implements NotusAttributeBuilder<T> {
   static final Map<String, NotusAttributeBuilder> _registry = {
     NotusAttribute.bold.key: NotusAttribute.bold,
     NotusAttribute.italic.key: NotusAttribute.italic,
+    NotusAttribute.underline.key: NotusAttribute.underline,
     NotusAttribute.link.key: NotusAttribute.link,
     NotusAttribute.heading.key: NotusAttribute.heading,
     NotusAttribute.block.key: NotusAttribute.block,
@@ -88,6 +89,9 @@ class NotusAttribute<T> implements NotusAttributeBuilder<T> {
   /// Italic style attribute.
   static const italic = _ItalicAttribute();
 
+  /// Underline style attribute.
+  static const underline = _UnderlineAttribute();
+
   /// Link style attribute.
   // ignore: const_eval_throws_exception
   static const link = LinkAttributeBuilder._();
@@ -332,6 +336,11 @@ class _ItalicAttribute extends NotusAttribute<bool> {
   const _ItalicAttribute() : super._('i', NotusAttributeScope.inline, true);
 }
 
+/// Applies underline style to a text segment.
+class _UnderlineAttribute extends NotusAttribute<bool> {
+  const _UnderlineAttribute() : super._('u', NotusAttributeScope.inline, true);
+}
+
 /// Builder for link attribute values.
 ///
 /// There is no need to use this class directly, consider using
diff --git a/packages/zefyr/lib/src/widgets/__theme.dart b/packages/zefyr/lib/src/widgets/__theme.dart
index a62d70028..0b9ac1371 100644
--- a/packages/zefyr/lib/src/widgets/__theme.dart
+++ b/packages/zefyr/lib/src/widgets/__theme.dart
@@ -54,6 +54,7 @@ class ZefyrTheme extends InheritedWidget {
 class ZefyrThemeData {
   final TextStyle boldStyle;
   final TextStyle italicStyle;
+  final TextStyle underlineStyle;
   final TextStyle linkStyle;
   final StyleTheme paragraphTheme;
   final HeadingTheme headingTheme;
@@ -75,12 +76,14 @@ class ZefyrThemeData {
     const padding = EdgeInsets.symmetric(vertical: 8.0);
     final boldStyle = TextStyle(fontWeight: FontWeight.bold);
     final italicStyle = TextStyle(fontStyle: FontStyle.italic);
+    final underlineStyle = TextStyle(decoration: TextDecoration.underline);
     final linkStyle = TextStyle(
         color: themeData.accentColor, decoration: TextDecoration.underline);
 
     return ZefyrThemeData(
       boldStyle: boldStyle,
       italicStyle: italicStyle,
+      underlineStyle: underlineStyle,
       linkStyle: linkStyle,
       paragraphTheme: StyleTheme(textStyle: paragraphStyle, padding: padding),
       headingTheme: HeadingTheme.fallback(context),
@@ -95,6 +98,7 @@ class ZefyrThemeData {
   const ZefyrThemeData({
     this.boldStyle,
     this.italicStyle,
+    this.underlineStyle,
     this.linkStyle,
     this.paragraphTheme,
     this.headingTheme,
@@ -109,6 +113,7 @@ class ZefyrThemeData {
     TextStyle textStyle,
     TextStyle boldStyle,
     TextStyle italicStyle,
+    TextStyle underlineStyle,
     TextStyle linkStyle,
     StyleTheme paragraphTheme,
     HeadingTheme headingTheme,
@@ -121,6 +126,7 @@ class ZefyrThemeData {
     return ZefyrThemeData(
       boldStyle: boldStyle ?? this.boldStyle,
       italicStyle: italicStyle ?? this.italicStyle,
+      underlineStyle: underlineStyle ?? this.underlineStyle,
       linkStyle: linkStyle ?? this.linkStyle,
       paragraphTheme: paragraphTheme ?? this.paragraphTheme,
       headingTheme: headingTheme ?? this.headingTheme,
@@ -136,6 +142,7 @@ class ZefyrThemeData {
     return copyWith(
       boldStyle: other.boldStyle,
       italicStyle: other.italicStyle,
+      underlineStyle: other.underlineStyle,
       linkStyle: other.linkStyle,
       paragraphTheme: other.paragraphTheme,
       headingTheme: other.headingTheme,
diff --git a/packages/zefyr/lib/src/widgets/common.dart b/packages/zefyr/lib/src/widgets/common.dart
index 2e5cbc4f9..058bc4bc3 100644
--- a/packages/zefyr/lib/src/widgets/common.dart
+++ b/packages/zefyr/lib/src/widgets/common.dart
@@ -145,6 +145,9 @@ class _ZefyrLineState extends State<ZefyrLine> {
     if (style.containsSame(NotusAttribute.italic)) {
       result = result.merge(theme.attributeTheme.italic);
     }
+    if (style.containsSame(NotusAttribute.underline)) {
+      result = result.merge(theme.attributeTheme.underline);
+    }
     if (style.contains(NotusAttribute.link)) {
       result = result.merge(theme.attributeTheme.link);
     }
diff --git a/packages/zefyr/lib/src/widgets/controller.dart b/packages/zefyr/lib/src/widgets/controller.dart
index 1117ab617..5350be6b6 100644
--- a/packages/zefyr/lib/src/widgets/controller.dart
+++ b/packages/zefyr/lib/src/widgets/controller.dart
@@ -167,7 +167,8 @@ class ZefyrController extends ChangeNotifier {
 
     if (length == 0 &&
         (attribute.key == NotusAttribute.bold.key ||
-            attribute.key == NotusAttribute.italic.key)) {
+            attribute.key == NotusAttribute.italic.key ||
+            attribute.key == NotusAttribute.underline.key)) {
       // Add the attribute to our toggledStyle. It will be used later upon insertion.
       _toggledStyles = toggledStyles.put(attribute);
     }
diff --git a/packages/zefyr/lib/src/widgets/theme.dart b/packages/zefyr/lib/src/widgets/theme.dart
index 70b063fbc..6cbd7dbff 100644
--- a/packages/zefyr/lib/src/widgets/theme.dart
+++ b/packages/zefyr/lib/src/widgets/theme.dart
@@ -287,6 +287,9 @@ class AttributeTheme {
   /// Style used to render "italic" text.
   final TextStyle italic;
 
+  /// Style used to render "underline" text.
+  final TextStyle underline;
+
   /// Style used to render text containing links.
   final TextStyle link;
 
@@ -315,6 +318,7 @@ class AttributeTheme {
   AttributeTheme({
     this.bold,
     this.italic,
+    this.underline,
     this.link,
     this.heading1,
     this.heading2,
@@ -347,6 +351,7 @@ class AttributeTheme {
     return AttributeTheme(
       bold: TextStyle(fontWeight: FontWeight.bold),
       italic: TextStyle(fontStyle: FontStyle.italic),
+      underline: TextStyle(decoration: TextDecoration.underline),
       link: TextStyle(
         decoration: TextDecoration.underline,
         color: theme.accentColor,
@@ -412,6 +417,7 @@ class AttributeTheme {
   AttributeTheme copyWith({
     TextStyle bold,
     TextStyle italic,
+    TextStyle underline,
     TextStyle link,
     LineTheme heading1,
     LineTheme heading2,
@@ -424,6 +430,7 @@ class AttributeTheme {
     return AttributeTheme(
       bold: bold ?? this.bold,
       italic: italic ?? this.italic,
+      underline: underline ?? this.underline,
       link: link ?? this.link,
       heading1: heading1 ?? this.heading1,
       heading2: heading2 ?? this.heading2,
@@ -442,6 +449,7 @@ class AttributeTheme {
     return copyWith(
       bold: bold?.merge(other.bold) ?? other.bold,
       italic: italic?.merge(other.italic) ?? other.italic,
+      underline: underline?.merge(other.underline) ?? other.underline,
       link: link?.merge(other.link) ?? other.link,
       heading1: heading1?.merge(other.heading1) ?? other.heading1,
       heading2: heading2?.merge(other.heading2) ?? other.heading2,
@@ -459,6 +467,7 @@ class AttributeTheme {
     final AttributeTheme otherTheme = other;
     return (otherTheme.bold == bold) &&
         (otherTheme.italic == italic) &&
+        (otherTheme.underline == underline) &&
         (otherTheme.link == link) &&
         (otherTheme.heading1 == heading1) &&
         (otherTheme.heading2 == heading2) &&
diff --git a/packages/zefyr/lib/src/widgets/toolbar.dart b/packages/zefyr/lib/src/widgets/toolbar.dart
index a5a1e33e4..1762fd438 100644
--- a/packages/zefyr/lib/src/widgets/toolbar.dart
+++ b/packages/zefyr/lib/src/widgets/toolbar.dart
@@ -15,6 +15,7 @@ import 'theme.dart';
 enum ZefyrToolbarAction {
   bold,
   italic,
+  underline,
   link,
   unlink,
   clipboardCopy,
@@ -39,6 +40,7 @@ enum ZefyrToolbarAction {
 final kZefyrToolbarAttributeActions = <ZefyrToolbarAction, NotusAttributeKey>{
   ZefyrToolbarAction.bold: NotusAttribute.bold,
   ZefyrToolbarAction.italic: NotusAttribute.italic,
+  ZefyrToolbarAction.underline: NotusAttribute.underline,
   ZefyrToolbarAction.link: NotusAttribute.link,
   ZefyrToolbarAction.heading: NotusAttribute.heading,
   ZefyrToolbarAction.headingLevel1: NotusAttribute.heading.level1,
@@ -252,6 +254,7 @@ class ZefyrToolbarState extends State<ZefyrToolbar>
     final buttons = <Widget>[
       buildButton(context, ZefyrToolbarAction.bold),
       buildButton(context, ZefyrToolbarAction.italic),
+      buildButton(context, ZefyrToolbarAction.underline),
       LinkButton(),
       HeadingButton(),
       buildButton(context, ZefyrToolbarAction.bulletList),
@@ -337,6 +340,7 @@ class _DefaultZefyrToolbarDelegate implements ZefyrToolbarDelegate {
   static const kDefaultButtonIcons = {
     ZefyrToolbarAction.bold: Icons.format_bold,
     ZefyrToolbarAction.italic: Icons.format_italic,
+    ZefyrToolbarAction.underline: Icons.format_underlined,
     ZefyrToolbarAction.link: Icons.link,
     ZefyrToolbarAction.unlink: Icons.link_off,
     ZefyrToolbarAction.clipboardCopy: Icons.content_copy,