--- a/toolkit/devtools/server/actors/webconsole.js
+++ b/toolkit/devtools/server/actors/webconsole.js
@@ -66,16 +66,17 @@ function WebConsoleActor(aConnection, aP
 
   this._prefs = {};
 
   this.dbg = this.parentActor.makeDebugger();
 
   this._netEvents = new Map();
   this._gripDepth = 0;
   this._listeners = new Set();
+  this._lastConsoleInputEvaluation = undefined;
 
   this._onWillNavigate = this._onWillNavigate.bind(this);
   this._onChangedToplevelDocument = this._onChangedToplevelDocument.bind(this);
   events.on(this.parentActor, "changed-toplevel-document", this._onChangedToplevelDocument);
   this._onObserverNotification = this._onObserverNotification.bind(this);
   if (this.parentActor.isRootActor) {
     Services.obs.addObserver(this._onObserverNotification,
                              "last-pb-context-exited", false);
@@ -353,16 +354,17 @@ WebConsoleActor.prototype =
     this.conn.removeActorPool(this._actorPool);
     if (this.parentActor.isRootActor) {
       Services.obs.removeObserver(this._onObserverNotification,
                                   "last-pb-context-exited");
     }
     this._actorPool = null;
 
     this._jstermHelpersCache = null;
+    this._lastConsoleInputEvaluation = null;
     this._evalWindow = null;
     this._netEvents.clear();
     this.dbg.enabled = false;
     this.dbg = null;
     this.conn = null;
   },
 
   /**
@@ -498,16 +500,27 @@ WebConsoleActor.prototype =
    * @param object aActor
    *        The actor instance you want to release.
    */
   releaseActor: function WCA_releaseActor(aActor)
   {
     this._actorPool.removeActor(aActor.actorID);
   },
 
+  /**
+   * Returns the latest web console input evaluation.
+   * This is undefined if no evaluations have been completed.
+   *
+   * @return object
+   */
+  getLastConsoleInputEvaluation: function WCU_getLastConsoleInputEvaluation()
+  {
+    return this._lastConsoleInputEvaluation;
+  },
+
   //////////////////
   // Request handlers for known packet types.
   //////////////////
 
   /**
    * Handler for the "startListeners" request.
    *
    * @param object aRequest
@@ -811,16 +824,18 @@ WebConsoleActor.prototype =
     // the console should remain functional.
     let resultGrip;
     try {
       resultGrip = this.createValueGrip(result);
     } catch (e) {
       errorMessage = e;
     }
 
+    this._lastConsoleInputEvaluation = result;
+
     return {
       from: this.actorID,
       input: input,
       result: resultGrip,
       timestamp: timestamp,
       exception: errorGrip,
       exceptionMessage: this._createStringGrip(errorMessage),
       helperResult: helperResult,

--- a/toolkit/devtools/webconsole/test/chrome.ini
+++ b/toolkit/devtools/webconsole/test/chrome.ini
@@ -10,20 +10,21 @@ support-files =
 [test_basics.html]
 [test_bug819670_getter_throws.html]
 [test_cached_messages.html]
 [test_consoleapi.html]
 [test_consoleapi_innerID.html]
 [test_file_uri.html]
 [test_reflow.html]
 [test_jsterm.html]
+[test_jsterm_cd_iframe.html]
+[test_jsterm_last_result.html]
 [test_network_get.html]
 [test_network_longstring.html]
 [test_network_post.html]
 [test_network_security-hpkp.html]
 [test_network_security-hsts.html]
 [test_nsiconsolemessage.html]
 [test_object_actor.html]
 [test_object_actor_native_getters.html]
 [test_object_actor_native_getters_lenient_this.html]
 [test_page_errors.html]
 [test_throw.html]
-[test_jsterm_cd_iframe.html]

--- a/toolkit/devtools/webconsole/test/common.js
+++ b/toolkit/devtools/webconsole/test/common.js
@@ -3,16 +3,20 @@
 
 "use strict";
 
 const {classes: Cc, interfaces: Ci, utils: Cu} = Components;
 
 const XHTML_NS = "http://www.w3.org/1999/xhtml";
 
 Cu.import("resource://gre/modules/Services.jsm");
+const {Task} = Cu.import("resource://gre/modules/Task.jsm", {});
+
+// This gives logging to stdout for tests
+var {console} = Cu.import("resource://gre/modules/devtools/Console.jsm", {});
 
 let devtools = Cu.import("resource://gre/modules/devtools/Loader.jsm", {}).devtools;
 let WebConsoleUtils = devtools.require("devtools/toolkit/webconsole/utils").Utils;
 
 let ConsoleAPIStorage = Cc["@mozilla.org/consoleAPI-storage;1"]
                           .getService(Ci.nsIConsoleAPIStorage);
 
 let {ConsoleServiceListener, ConsoleAPIListener} =

new file mode 100644
--- /dev/null
+++ b/toolkit/devtools/webconsole/test/test_jsterm_last_result.html
@@ -0,0 +1,130 @@
+<!DOCTYPE HTML>
+<html lang="en">
+<head>
+  <meta charset="utf8">
+  <title>Test for the $_ getter</title>
+  <script type="text/javascript" src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript;version=1.8" src="common.js"></script>
+  <!-- Any copyright is dedicated to the Public Domain.
+     - http://creativecommons.org/publicdomain/zero/1.0/ -->
+</head>
+<body>
+<p>Test for the $_ getter</p>
+
+<iframe id="content-iframe" src="http://example.com/chrome/toolkit/devtools/webconsole/test/sandboxed_iframe.html"></iframe>
+
+<script class="testbody" type="text/javascript;version=1.8">
+SimpleTest.waitForExplicitFinish();
+let gState;
+
+function evaluateJS(input, callback) {
+  return new Promise((resolve, reject) => {
+    gState.client.evaluateJSAsync(input, response => {
+      if (callback) {
+        callback(response);
+      }
+      resolve(response);
+    });
+  });
+}
+
+function startTest()
+{
+  removeEventListener("load", startTest);
+  attachConsole([], state => {
+    gState = state;
+    let tests = [checkUndefinedResult,checkAdditionResult,checkObjectResult];
+    runTests(tests, testEnd);
+  }, true);
+}
+
+let checkUndefinedResult = Task.async(function*() {
+  info ("$_ returns undefined if nothing has evaluated yet");
+  let response = yield evaluateJS("$_");
+  basicResultCheck(response, "$_", undefined);
+  nextTest();
+});
+
+let checkAdditionResult = Task.async(function*() {
+  info ("$_ returns last value and performs basic arithmetic");
+  let response = yield evaluateJS("2+2");
+  basicResultCheck(response, "2+2", 4);
+
+  response = yield evaluateJS("$_");
+  basicResultCheck(response, "$_", 4);
+
+  response = yield evaluateJS("$_ + 2");
+  basicResultCheck(response, "$_ + 2", 6);
+
+  response = yield evaluateJS("$_ + 4");
+  basicResultCheck(response, "$_ + 4", 10);
+
+  nextTest();
+});
+
+let checkObjectResult = Task.async(function*() {
+  info ("$_ has correct references to objects");
+
+  let response = yield evaluateJS("var foo = {bar:1}; foo;");
+  basicResultCheck(response, "var foo = {bar:1}; foo;", {
+    type: "object",
+    class: "Object",
+    actor: /[a-z]/,
+  });
+  checkObject(response.result.preview.ownProperties, {
+    bar: {
+      value: 1
+    }
+  });
+
+  response = yield evaluateJS("$_");
+  basicResultCheck(response, "$_", {
+    type: "object",
+    class: "Object",
+    actor: /[a-z]/,
+  });
+  checkObject(response.result.preview.ownProperties, {
+    bar: {
+      value: 1
+    }
+  });
+
+  top.foo.bar = 2;
+
+  response = yield evaluateJS("$_");
+  basicResultCheck(response, "$_", {
+    type: "object",
+    class: "Object",
+    actor: /[a-z]/,
+  });
+  checkObject(response.result.preview.ownProperties, {
+    bar: {
+      value: 2
+    }
+  });
+
+  nextTest();
+});
+
+function basicResultCheck(response, input, output) {
+  checkObject(response, {
+    from: gState.actor,
+    input: input,
+    result: output,
+  });
+  ok(!response.exception, "no eval exception");
+  ok(!response.helperResult, "no helper result");
+}
+
+function testEnd()
+{
+  closeDebugger(gState, function() {
+    gState = null;
+    SimpleTest.finish();
+  });
+}
+
+addEventListener("load", startTest);
+</script>
+</body>
+</html>

--- a/toolkit/devtools/webconsole/utils.js
+++ b/toolkit/devtools/webconsole/utils.js
@@ -1545,16 +1545,30 @@ function JSTermHelpers(aOwner)
    *         Returns the result of document.querySelectorAll(aSelector).
    */
   aOwner.sandbox.$$ = function JSTH_$$(aSelector)
   {
     return aOwner.window.document.querySelectorAll(aSelector);
   };
 
   /**
+   * Returns the result of the last console input evaluation
+   *
+   * @return object|undefined
+   * Returns last console evaluation or undefined
+   */
+  Object.defineProperty(aOwner.sandbox, "$_", {
+    get: function() {
+      return aOwner.consoleActor.getLastConsoleInputEvaluation();
+    },
+    enumerable: true,
+    configurable: true
+  });
+
+  /**
    * Runs an xPath query and returns all matched nodes.
    *
    * @param string aXPath
    *        xPath search query to execute.
    * @param [optional] nsIDOMNode aContext
    *        Context to run the xPath query on. Uses window.document if not set.
    * @return array of nsIDOMNode
    */