diff --git a/app/components/gh-markdown-editor.js b/app/components/gh-markdown-editor.js
index bd1e188366..293583ac95 100644
--- a/app/components/gh-markdown-editor.js
+++ b/app/components/gh-markdown-editor.js
@@ -106,6 +106,14 @@ export default Component.extend({
                     title: 'Toggle Fullscreen'
                 },
                 '|',
+                {
+                    name: 'spellcheck',
+                    action: () => {
+                        this._toggleSpellcheck();
+                    },
+                    className: 'fa fa-check',
+                    title: 'Toggle Spellcheck'
+                },
                 {
                     name: 'guide',
                     action: () => {
@@ -199,11 +207,12 @@ export default Component.extend({
         cm.replaceSelection(text, 'end');
     },
 
-    // mark the split-pane/full-screen buttons active when they're active
+    // mark the split-pane/full-screen/spellcheck buttons active when they're active
     _updateButtonState() {
         if (this._editor) {
             let fullScreenButton = this._editor.toolbarElements.fullscreen;
             let sideBySideButton = this._editor.toolbarElements['side-by-side'];
+            let spellcheckButton = this._editor.toolbarElements.spellcheck;
 
             if (this.get('_isFullScreen')) {
                 fullScreenButton.classList.add('active');
@@ -216,6 +225,12 @@ export default Component.extend({
             } else {
                 sideBySideButton.classList.remove('active');
             }
+
+            if (this._editor.codemirror.getOption('mode') === 'spell-checker') {
+                spellcheckButton.classList.add('active');
+            } else {
+                spellcheckButton.classList.remove('active');
+            }
         }
     },
 
@@ -305,6 +320,18 @@ export default Component.extend({
         this._editor.togglePreview();
     },
 
+    _toggleSpellcheck() {
+        let cm = this._editor.codemirror;
+
+        if (cm.getOption('mode') === 'spell-checker') {
+            cm.setOption('mode', 'markdown');
+        } else {
+            cm.setOption('mode', 'spell-checker');
+        }
+
+        this._updateButtonState();
+    },
+
     willDestroyElement() {
         if (this.get('_isSplitScreen')) {
             this._disconnectSplitPreview();
diff --git a/app/styles/layouts/editor.css b/app/styles/layouts/editor.css
index 91867c3843..5ea5d5fda8 100644
--- a/app/styles/layouts/editor.css
+++ b/app/styles/layouts/editor.css
@@ -381,3 +381,25 @@
 .editor-toolbar a.disabled:hover {
     border: none;
 }
+
+.editor-toolbar .fa-check {
+    position: relative;
+    vertical-align: bottom;
+}
+.editor-toolbar .fa-check:before {
+    font-size: 14px;
+    position: absolute;
+    line-height: 14px;
+    right: 3px;
+    bottom: 4px;
+}
+
+.editor-toolbar .fa-check:after {
+    content: 'abc';
+    font-family: var(--font-family);
+    position: absolute;
+    left: 4px;
+    font-size: 9px;
+    top: 6px;
+    line-height: 9px;
+}
diff --git a/yarn.lock b/yarn.lock
index 8d51afe085..52aa332bad 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -7458,7 +7458,7 @@ simple-is@~0.2.0:
 
 "simplemde@https://github.com/kevinansfield/simplemde-markdown-editor.git#ghost":
   version "1.11.2"
-  resolved "https://github.com/kevinansfield/simplemde-markdown-editor.git#29f69b859b19f6ecbc678780290e388298b308c4"
+  resolved "https://github.com/kevinansfield/simplemde-markdown-editor.git#05ba8d8ff395b148258743a31ef7e07ae5579d3e"
   dependencies:
     codemirror "*"
     codemirror-spell-checker "*"