diff --git a/gulpfile.js b/gulpfile.js
index e1fd6f369..ccb9ed072 100644
--- a/gulpfile.js
+++ b/gulpfile.js
@@ -33,6 +33,7 @@ module.exports = {
   buildGenerators: buildTasks.generators,
   buildAdvancedCompilationTest: buildTasks.advancedCompilationTest,
   checkinBuilt: buildTasks.checkinBuilt,
+  clean: buildTasks.cleanBuildDir,
   gitSyncDevelop: gitTasks.syncDevelop,
   gitSyncMaster: gitTasks.syncMaster,
   gitCreateRC: gitTasks.createRC,
diff --git a/package.json b/package.json
index ad0401410..81925ec18 100644
--- a/package.json
+++ b/package.json
@@ -29,6 +29,7 @@
     "build:langfiles": "gulp buildLangfiles",
     "build:uncompressed": "gulp buildUncompressed",
     "bump": "npm --no-git-tag-version version 4.$(date +'%Y%m%d').0",
+    "clean": "gulp clean",
     "checkin": "gulp checkinBuilt",
     "deployDemos": "gulp deployDemos",
     "format": "git-clang-format",
diff --git a/scripts/gulpfiles/build_tasks.js b/scripts/gulpfiles/build_tasks.js
index 41b41a962..e87b1cf69 100644
--- a/scripts/gulpfiles/build_tasks.js
+++ b/scripts/gulpfiles/build_tasks.js
@@ -21,6 +21,8 @@ var through2 = require('through2');
 var closureCompiler = require('google-closure-compiler').gulp();
 var closureDeps = require('google-closure-deps');
 var argv = require('yargs').argv;
+var rimraf = require('rimraf');
+
 var {BUILD_DIR} = require('./config');
 var {getPackageJson} = require('./helper_tasks');
 
@@ -549,6 +551,18 @@ function checkinBuilt() {
   ]).pipe(gulp.dest('.'));
 };
 
+/**
+ * This task cleans the build directory (by deleting it).
+ */
+function cleanBuildDir(done) {
+  // Sanity check.
+  if (BUILD_DIR === '.' || BUILD_DIR === '/') {
+    throw new Error(`Refusing to rm -rf ${BUILD_DIR}`);
+  }
+  rimraf.sync(BUILD_DIR);
+  done();
+}
+
 module.exports = {
   build: build,
   core: buildCore,
@@ -559,5 +573,6 @@ module.exports = {
   compressed: buildCompressed,
   generators: buildGenerators,
   checkinBuilt: checkinBuilt,
+  cleanBuildDir: cleanBuildDir,
   advancedCompilationTest: buildAdvancedCompilationTest,
 }