diff --git a/demo/index.html b/demo/index.html
index 93399f9c..da348f5e 100644
--- a/demo/index.html
+++ b/demo/index.html
@@ -23,6 +23,9 @@
           <p>
             <label><input type="checkbox" id="option-cursor-blink"> cursorBlink</label>
           </p>
+          <p>
+            <label><input type="checkbox" id="option-mac-option-is-meta"> macOptionIsMeta</label>
+          </p>
           <p>
             <label>
               cursorStyle
diff --git a/demo/main.js b/demo/main.js
index 95b15a0d..1faf77d8 100644
--- a/demo/main.js
+++ b/demo/main.js
@@ -27,6 +27,7 @@ var terminalContainer = document.getElementById('terminal-container'),
     optionElements = {
       cursorBlink: document.querySelector('#option-cursor-blink'),
       cursorStyle: document.querySelector('#option-cursor-style'),
+      macOptionIsMeta: document.querySelector('#option-mac-option-is-meta'),
       scrollback: document.querySelector('#option-scrollback'),
       tabstopwidth: document.querySelector('#option-tabstopwidth'),
       bellStyle: document.querySelector('#option-bell-style')
@@ -72,6 +73,9 @@ optionElements.cursorStyle.addEventListener('change', function () {
 optionElements.bellStyle.addEventListener('change', function () {
   term.setOption('bellStyle', optionElements.bellStyle.value);
 });
+optionElements.macOptionIsMeta.addEventListener('change', function () {
+  term.setOption('macOptionIsMeta', optionElements.macOptionIsMeta.checked);
+});
 optionElements.scrollback.addEventListener('change', function () {
   term.setOption('scrollback', parseInt(optionElements.scrollback.value, 10));
 });
@@ -87,6 +91,7 @@ function createTerminal() {
     terminalContainer.removeChild(terminalContainer.children[0]);
   }
   term = new Terminal({
+    macOptionIsMeta: optionElements.macOptionIsMeta.enabled,
     cursorBlink: optionElements.cursorBlink.checked,
     scrollback: parseInt(optionElements.scrollback.value, 10),
     tabStopWidth: parseInt(optionElements.tabstopwidth.value, 10)
diff --git a/fixtures/typings-test/typings-test.ts b/fixtures/typings-test/typings-test.ts
index 5a5f6c50..0a88bd37 100644
--- a/fixtures/typings-test/typings-test.ts
+++ b/fixtures/typings-test/typings-test.ts
@@ -144,6 +144,7 @@ namespace methods_core {
       const r20: string = t.getOption('bellStyle');
       const r21: boolean = t.getOption('enableBold');
       const r22: number = t.getOption('letterSpacing');
+      const r23: boolean = t.getOption('macOptionIsMeta');
     }
     {
       const t: Terminal = new Terminal();
@@ -177,6 +178,7 @@ namespace methods_core {
       t.setOption('lineHeight', 1);
       t.setOption('fontFamily', 'foo');
       t.setOption('theme', {background: '#ff0000'});
+      t.setOption('macOptionIsMeta', true);
     }
   }
   namespace scrolling {
diff --git a/src/Interfaces.ts b/src/Interfaces.ts
index 780a4047..70b8509f 100644
--- a/src/Interfaces.ts
+++ b/src/Interfaces.ts
@@ -143,6 +143,7 @@ export interface ITerminalOptions {
   handler?: (data: string) => void;
   letterSpacing?: number;
   lineHeight?: number;
+  macOptionIsMeta?: boolean;
   rows?: number;
   screenKeys?: boolean;
   scrollback?: number;
diff --git a/src/Terminal.test.ts b/src/Terminal.test.ts
index 9cb0b75c..946e9efb 100644
--- a/src/Terminal.test.ts
+++ b/src/Terminal.test.ts
@@ -503,6 +503,9 @@ describe('term.js addons', () => {
       it('should return \\x1b[5C for alt+right', () => {
         assert.equal(term.evaluateKeyEscapeSequence({ altKey: true, keyCode: 39 }).key, '\x1b[1;5C'); // CSI 5 C
       });
+      it('should return \\x1ba for alt+a', () => {
+        assert.equal(term.evaluateKeyEscapeSequence({ altKey: true, keyCode: 65 }).key, '\x1ba');
+      });
     });
 
     describe('On macOS platforms', () => {
@@ -515,6 +518,19 @@ describe('term.js addons', () => {
       it('should return \\x1bf for alt+right', () => {
         assert.equal(term.evaluateKeyEscapeSequence({ altKey: true, keyCode: 39 }).key, '\x1bf'); // CSI 5 C
       });
+      it('should return undefined for alt+a', () => {
+        assert.strictEqual(term.evaluateKeyEscapeSequence({ altKey: true, keyCode: 65 }).key, undefined);
+      });
+    });
+
+    describe('with macOptionIsMeta', () => {
+      beforeEach(() => {
+        term.browser.isMac = true;
+        term.setOption('macOptionIsMeta', true);
+      });
+      it('should return \\x1ba for alt+a', () => {
+        assert.equal(term.evaluateKeyEscapeSequence({ altKey: true, keyCode: 65 }).key, '\x1ba');
+      });
     });
 
     it('should return \\x1b[5A for alt+up', () => {
@@ -597,6 +613,22 @@ describe('term.js addons', () => {
       };
     });
 
+    describe('with macOptionIsMeta', () => {
+      beforeEach(() => {
+        term.browser.isMac = true;
+        term.setOption('macOptionIsMeta', true);
+      });
+
+      it('should interfere with the alt key on keyDown', () => {
+        evKeyDown.altKey = true;
+        evKeyDown.keyCode = 81;
+        assert.equal(term.keyDown(evKeyDown), false);
+        evKeyDown.altKey = true;
+        evKeyDown.keyCode = 192;
+        assert.equal(term.keyDown(evKeyDown), false);
+      });
+    });
+
     describe('On Mac OS', () => {
       beforeEach(() => {
         term.browser.isMac = true;
diff --git a/src/Terminal.ts b/src/Terminal.ts
index 31c9a250..b56caf83 100644
--- a/src/Terminal.ts
+++ b/src/Terminal.ts
@@ -80,6 +80,7 @@ const DEFAULT_OPTIONS: ITerminalOptions = {
   scrollback: 1000,
   screenKeys: false,
   debug: false,
+  macOptionIsMeta: false,
   cancelEvents: false,
   disableStdin: false,
   useFlowControl: false,
@@ -1374,7 +1375,7 @@ export class Terminal extends EventEmitter implements ITerminal, IInputHandlingT
       return this.cancel(ev, true);
     }
 
-    if (isThirdLevelShift(this.browser, ev)) {
+    if (this._isThirdLevelShift(this.browser, ev)) {
       return true;
     }
 
@@ -1395,6 +1396,19 @@ export class Terminal extends EventEmitter implements ITerminal, IInputHandlingT
     return this.cancel(ev, true);
   }
 
+  private _isThirdLevelShift(browser: IBrowser, ev: KeyboardEvent): boolean {
+    const thirdLevelKey =
+        (browser.isMac && !this.options.macOptionIsMeta && ev.altKey && !ev.ctrlKey && !ev.metaKey) ||
+        (browser.isMSWindows && ev.altKey && ev.ctrlKey && !ev.metaKey);
+
+    if (ev.type === 'keypress') {
+      return thirdLevelKey;
+    }
+
+    // Don't invoke for arrows, pageDown, home, backspace, etc. (on non-keypress events)
+    return thirdLevelKey && (!ev.keyCode || ev.keyCode > 47);
+  }
+
   /**
    * Returns an object that determines how a KeyboardEvent should be handled. The key of the
    * returned value is the new key code to pass to the PTY.
@@ -1699,8 +1713,8 @@ export class Terminal extends EventEmitter implements ITerminal, IInputHandlingT
             // ^] - Operating System Command (OSC)
             result.key = String.fromCharCode(29);
           }
-        } else if (!this.browser.isMac && ev.altKey && !ev.ctrlKey && !ev.metaKey) {
-          // On Mac this is a third level shift. Use <Esc> instead.
+        } else if ((!this.browser.isMac || this.options.macOptionIsMeta) && ev.altKey && !ev.ctrlKey && !ev.metaKey) {
+          // On macOS this is a third level shift when !macOptionIsMeta. Use <Esc> instead.
           if (ev.keyCode >= 65 && ev.keyCode <= 90) {
             result.key = C0.ESC + String.fromCharCode(ev.keyCode + 32);
           } else if (ev.keyCode === 192) {
@@ -1766,7 +1780,7 @@ export class Terminal extends EventEmitter implements ITerminal, IInputHandlingT
     }
 
     if (!key || (
-      (ev.altKey || ev.ctrlKey || ev.metaKey) && !isThirdLevelShift(this.browser, ev)
+      (ev.altKey || ev.ctrlKey || ev.metaKey) && !this._isThirdLevelShift(this.browser, ev)
     )) {
       return false;
     }
@@ -2158,19 +2172,6 @@ function off(el: any, type: string, handler: (event: Event) => any, capture: boo
   el.removeEventListener(type, handler, capture);
 }
 
-function isThirdLevelShift(browser: IBrowser, ev: KeyboardEvent): boolean {
-  const thirdLevelKey =
-      (browser.isMac && ev.altKey && !ev.ctrlKey && !ev.metaKey) ||
-      (browser.isMSWindows && ev.altKey && ev.ctrlKey && !ev.metaKey);
-
-  if (ev.type === 'keypress') {
-    return thirdLevelKey;
-  }
-
-  // Don't invoke for arrows, pageDown, home, backspace, etc. (on non-keypress events)
-  return thirdLevelKey && (!ev.keyCode || ev.keyCode > 47);
-}
-
 function wasMondifierKeyOnlyEvent(ev: KeyboardEvent): boolean {
   return ev.keyCode === 16 || // Shift
     ev.keyCode === 17 || // Ctrl
diff --git a/typings/xterm.d.ts b/typings/xterm.d.ts
index 83199e08..43842bad 100644
--- a/typings/xterm.d.ts
+++ b/typings/xterm.d.ts
@@ -454,7 +454,7 @@ declare module 'xterm' {
      * @param key The option key.
      * @param value The option value.
      */
-    setOption(key: 'cancelEvents' | 'convertEol' | 'cursorBlink' | 'debug' | 'disableStdin' | 'enableBold' | 'popOnBell' | 'screenKeys' | 'useFlowControl' | 'visualBell', value: boolean): void;
+    setOption(key: 'cancelEvents' | 'convertEol' | 'cursorBlink' | 'debug' | 'disableStdin' | 'enableBold' | 'macOptionIsMeta' | 'popOnBell' | 'screenKeys' | 'useFlowControl' | 'visualBell', value: boolean): void;
     /**
      * Sets an option on the terminal.
      * @param key The option key.