diff --git a/packages/react-is/README.md b/packages/react-is/README.md
new file mode 100644
index 0000000000000..f744d7d1de708
--- /dev/null
+++ b/packages/react-is/README.md
@@ -0,0 +1,83 @@
+# `react-is`
+
+This package allows you to test arbitrary values and see if they're a particular React type, e.g. React Elements.
+
+## Installation
+
+```sh
+# Yarn
+yarn add react-is
+
+# NPM
+npm install react-is --save
+```
+
+## Usage
+
+### AsyncMode
+
+```js
+import React from "react";
+import * as ReactIs from 'react-is';
+
+ReactIs.isAsyncMode(<React.unstable_AsyncMode />); // true
+ReactIs.typeOf(<React.unstable_AsyncMode />) === ReactIs.AsyncMode; // true
+```
+
+### Context
+
+```js
+import React from "react";
+import * as ReactIs from 'react-is';
+
+const ThemeContext = React.createContext("blue");
+
+ReactIs.isContextConsumer(<ThemeContext.Consumer />); // true
+ReactIs.isContextProvider(<ThemeContext.Provider />); // true
+ReactIs.typeOf(<ThemeContext.Provider />) === ReactIs.ContextProvider; // true
+ReactIs.typeOf(<ThemeContext.Consumer />) === ReactIs.ContextConsumer; // true
+```
+
+### Element
+
+```js
+import React from "react";
+import * as ReactIs from 'react-is';
+
+ReactIs.isElement(<div />); // true
+ReactIs.typeOf(<div />) === ReactIs.Element; // true
+```
+
+### Fragment
+
+```js
+import React from "react";
+import * as ReactIs from 'react-is';
+
+ReactIs.isFragment(<></>); // true
+ReactIs.typeOf(<></>) === ReactIs.Fragment; // true
+```
+
+### Portal
+
+```js
+import React from "react";
+import ReactDOM from "react-dom";
+import * as ReactIs from 'react-is';
+
+const div = document.createElement("div");
+const portal = ReactDOM.createPortal(<div />, div);
+
+ReactIs.isPortal(portal); // true
+ReactIs.typeOf(portal) === ReactIs.Portal; // true
+```
+
+### StrictMode
+
+```js
+import React from "react";
+import * as ReactIs from 'react-is';
+
+ReactIs.isStrictMode(<React.StrictMode />); // true
+ReactIs.typeOf(<React.StrictMode />) === ReactIs.StrictMode; // true
+```
diff --git a/packages/react-is/index.js b/packages/react-is/index.js
new file mode 100644
index 0000000000000..f8c9ffdcd287c
--- /dev/null
+++ b/packages/react-is/index.js
@@ -0,0 +1,12 @@
+/**
+ * Copyright (c) 2013-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ */
+
+'use strict';
+
+export * from './src/ReactIs';
diff --git a/packages/react-is/npm/index.js b/packages/react-is/npm/index.js
new file mode 100644
index 0000000000000..3ae098d078776
--- /dev/null
+++ b/packages/react-is/npm/index.js
@@ -0,0 +1,7 @@
+'use strict';
+
+if (process.env.NODE_ENV === 'production') {
+  module.exports = require('./cjs/react-is.production.min.js');
+} else {
+  module.exports = require('./cjs/react-is.development.js');
+}
diff --git a/packages/react-is/package.json b/packages/react-is/package.json
new file mode 100644
index 0000000000000..8fd899a90e05b
--- /dev/null
+++ b/packages/react-is/package.json
@@ -0,0 +1,23 @@
+{
+  "name": "react-is",
+  "version": "16.3.0-alpha.0",
+  "description": "Brand checking of React Elements.",
+  "main": "index.js",
+  "repository": "facebook/react",
+  "keywords": ["react"],
+  "license": "MIT",
+  "bugs": {
+    "url": "https://github.com/facebook/react/issues"
+  },
+  "homepage": "https://reactjs.org/",
+  "peerDependencies": {
+    "react": "^16.0.0 || 16.3.0-alpha.0"
+  },
+  "files": [
+    "LICENSE",
+    "README.md",
+    "index.js",
+    "cjs/",
+    "umd/"
+  ]
+}
\ No newline at end of file
diff --git a/packages/react-is/src/ReactIs.js b/packages/react-is/src/ReactIs.js
new file mode 100644
index 0000000000000..d26bc82f5e8c1
--- /dev/null
+++ b/packages/react-is/src/ReactIs.js
@@ -0,0 +1,86 @@
+/**
+ * Copyright (c) 2013-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ */
+
+'use strict';
+
+import {
+  REACT_ASYNC_MODE_TYPE,
+  REACT_CONTEXT_TYPE,
+  REACT_ELEMENT_TYPE,
+  REACT_FRAGMENT_TYPE,
+  REACT_PORTAL_TYPE,
+  REACT_PROVIDER_TYPE,
+  REACT_STRICT_MODE_TYPE,
+} from 'shared/ReactSymbols';
+
+export function typeOf(object: any) {
+  if (typeof object === 'object' && object !== null) {
+    const $$typeof = object.$$typeof;
+
+    switch ($$typeof) {
+      case REACT_ELEMENT_TYPE:
+        const type = object.type;
+
+        switch (type) {
+          case REACT_ASYNC_MODE_TYPE:
+          case REACT_FRAGMENT_TYPE:
+          case REACT_STRICT_MODE_TYPE:
+            return type;
+          default:
+            const $$typeofType = type.$$typeof;
+
+            switch ($$typeofType) {
+              case REACT_CONTEXT_TYPE:
+              case REACT_PROVIDER_TYPE:
+                return $$typeofType;
+              default:
+                return $$typeof;
+            }
+        }
+      case REACT_PORTAL_TYPE:
+        return $$typeof;
+    }
+  }
+
+  return undefined;
+}
+
+export const AsyncMode = REACT_ASYNC_MODE_TYPE;
+export const ContextConsumer = REACT_CONTEXT_TYPE;
+export const ContextProvider = REACT_PROVIDER_TYPE;
+export const Element = REACT_ELEMENT_TYPE;
+export const Fragment = REACT_FRAGMENT_TYPE;
+export const Portal = REACT_PORTAL_TYPE;
+export const StrictMode = REACT_STRICT_MODE_TYPE;
+
+export function isAsyncMode(object: any) {
+  return typeOf(object) === REACT_ASYNC_MODE_TYPE;
+}
+export function isContextConsumer(object: any) {
+  return typeOf(object) === REACT_CONTEXT_TYPE;
+}
+export function isContextProvider(object: any) {
+  return typeOf(object) === REACT_PROVIDER_TYPE;
+}
+export function isElement(object: any) {
+  return (
+    typeof object === 'object' &&
+    object !== null &&
+    object.$$typeof === REACT_ELEMENT_TYPE
+  );
+}
+export function isFragment(object: any) {
+  return typeOf(object) === REACT_FRAGMENT_TYPE;
+}
+export function isPortal(object: any) {
+  return typeOf(object) === REACT_PORTAL_TYPE;
+}
+export function isStrictMode(object: any) {
+  return typeOf(object) === REACT_STRICT_MODE_TYPE;
+}
diff --git a/packages/react-is/src/__tests__/ReactIs-test.js b/packages/react-is/src/__tests__/ReactIs-test.js
new file mode 100644
index 0000000000000..6200388fd525d
--- /dev/null
+++ b/packages/react-is/src/__tests__/ReactIs-test.js
@@ -0,0 +1,103 @@
+/**
+ * Copyright (c) 2013-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @emails react-core
+ */
+
+'use strict';
+
+let React;
+let ReactDOM;
+let ReactIs;
+
+describe('ReactIs', () => {
+  beforeEach(() => {
+    jest.resetModules();
+
+    React = require('react');
+    ReactDOM = require('react-dom');
+    ReactIs = require('react-is');
+  });
+
+  it('should return undefined for unknown/invalid types', () => {
+    expect(ReactIs.typeOf('abc')).toBe(undefined);
+    expect(ReactIs.typeOf(true)).toBe(undefined);
+    expect(ReactIs.typeOf(123)).toBe(undefined);
+    expect(ReactIs.typeOf({})).toBe(undefined);
+    expect(ReactIs.typeOf(null)).toBe(undefined);
+    expect(ReactIs.typeOf(undefined)).toBe(undefined);
+  });
+
+  it('should identify async mode', () => {
+    expect(ReactIs.typeOf(<React.unstable_AsyncMode />)).toBe(
+      ReactIs.AsyncMode,
+    );
+    expect(ReactIs.isAsyncMode(<React.unstable_AsyncMode />)).toBe(true);
+    expect(ReactIs.isAsyncMode({type: ReactIs.AsyncMode})).toBe(false);
+    expect(ReactIs.isAsyncMode(<React.StrictMode />)).toBe(false);
+    expect(ReactIs.isAsyncMode(<div />)).toBe(false);
+  });
+
+  it('should identify context consumers', () => {
+    const Context = React.createContext(false);
+    expect(ReactIs.typeOf(<Context.Consumer />)).toBe(ReactIs.ContextConsumer);
+    expect(ReactIs.isContextConsumer(<Context.Consumer />)).toBe(true);
+    expect(ReactIs.isContextConsumer(<Context.Provider />)).toBe(false);
+    expect(ReactIs.isContextConsumer(<div />)).toBe(false);
+  });
+
+  it('should identify context providers', () => {
+    const Context = React.createContext(false);
+    expect(ReactIs.typeOf(<Context.Provider />)).toBe(ReactIs.ContextProvider);
+    expect(ReactIs.isContextProvider(<Context.Provider />)).toBe(true);
+    expect(ReactIs.isContextProvider(<Context.Consumer />)).toBe(false);
+    expect(ReactIs.isContextProvider(<div />)).toBe(false);
+  });
+
+  it('should identify elements', () => {
+    expect(ReactIs.typeOf(<div />)).toBe(ReactIs.Element);
+    expect(ReactIs.isElement(<div />)).toBe(true);
+    expect(ReactIs.isElement('div')).toBe(false);
+    expect(ReactIs.isElement(true)).toBe(false);
+    expect(ReactIs.isElement(123)).toBe(false);
+    expect(ReactIs.isElement(null)).toBe(false);
+    expect(ReactIs.isElement(undefined)).toBe(false);
+    expect(ReactIs.isElement({})).toBe(false);
+
+    // It should also identify more specific types as elements
+    const Context = React.createContext(false);
+    expect(ReactIs.isElement(<Context.Provider />)).toBe(true);
+    expect(ReactIs.isElement(<Context.Consumer />)).toBe(true);
+    expect(ReactIs.isElement(<React.Fragment />)).toBe(true);
+    expect(ReactIs.isElement(<React.unstable_AsyncMode />)).toBe(true);
+    expect(ReactIs.isElement(<React.StrictMode />)).toBe(true);
+  });
+
+  it('should identify fragments', () => {
+    expect(ReactIs.typeOf(<React.Fragment />)).toBe(ReactIs.Fragment);
+    expect(ReactIs.isFragment(<React.Fragment />)).toBe(true);
+    expect(ReactIs.isFragment({type: ReactIs.Fragment})).toBe(false);
+    expect(ReactIs.isFragment('React.Fragment')).toBe(false);
+    expect(ReactIs.isFragment(<div />)).toBe(false);
+    expect(ReactIs.isFragment([])).toBe(false);
+  });
+
+  it('should identify portals', () => {
+    const div = document.createElement('div');
+    const portal = ReactDOM.createPortal(<div />, div);
+    expect(ReactIs.typeOf(portal)).toBe(ReactIs.Portal);
+    expect(ReactIs.isPortal(portal)).toBe(true);
+    expect(ReactIs.isPortal(div)).toBe(false);
+  });
+
+  it('should identify strict mode', () => {
+    expect(ReactIs.typeOf(<React.StrictMode />)).toBe(ReactIs.StrictMode);
+    expect(ReactIs.isStrictMode(<React.StrictMode />)).toBe(true);
+    expect(ReactIs.isStrictMode({type: ReactIs.StrictMode})).toBe(false);
+    expect(ReactIs.isStrictMode(<React.unstable_AsyncMode />)).toBe(false);
+    expect(ReactIs.isStrictMode(<div />)).toBe(false);
+  });
+});
diff --git a/scripts/rollup/bundles.js b/scripts/rollup/bundles.js
index ff57b766998e0..b29c382d51d15 100644
--- a/scripts/rollup/bundles.js
+++ b/scripts/rollup/bundles.js
@@ -234,6 +234,16 @@ const bundles = [
     global: 'ReactCallReturn',
     externals: [],
   },
+
+  /******* React Is *******/
+  {
+    label: 'react-is',
+    bundleTypes: [NODE_DEV, NODE_PROD, UMD_DEV, UMD_PROD],
+    moduleType: ISOMORPHIC,
+    entry: 'react-is',
+    global: 'ReactIs',
+    externals: [],
+  },
 ];
 
 // Based on deep-freeze by substack (public domain)
diff --git a/scripts/rollup/results.json b/scripts/rollup/results.json
index 78fc29e1035e8..57d2013e37f29 100644
--- a/scripts/rollup/results.json
+++ b/scripts/rollup/results.json
@@ -398,6 +398,34 @@
       "packageName": "react-reconciler",
       "size": 41327,
       "gzip": 13133
+    },
+    {
+      "filename": "react-is.development.js",
+      "bundleType": "NODE_DEV",
+      "packageName": "react-is",
+      "size": 3358,
+      "gzip": 1015
+    },
+    {
+      "filename": "react-is.production.min.js",
+      "bundleType": "NODE_PROD",
+      "packageName": "react-is",
+      "size": 1433,
+      "gzip": 607
+    },
+    {
+      "filename": "react-is.development.js",
+      "bundleType": "UMD_DEV",
+      "packageName": "react-is",
+      "size": 3547,
+      "gzip": 1071
+    },
+    {
+      "filename": "react-is.production.min.js",
+      "bundleType": "UMD_PROD",
+      "packageName": "react-is",
+      "size": 1515,
+      "gzip": 670
     }
   ]
 }
\ No newline at end of file
diff --git a/scripts/rollup/validate/eslintrc.umd.js b/scripts/rollup/validate/eslintrc.umd.js
index bfc5396ce52ec..7ee1e112f2b09 100644
--- a/scripts/rollup/validate/eslintrc.umd.js
+++ b/scripts/rollup/validate/eslintrc.umd.js
@@ -17,6 +17,7 @@ module.exports = {
     // UMD wrapper code
     // TODO: this is too permissive.
     // Ideally we should only allow these *inside* the UMD wrapper.
+    exports: true,
     module: true,
     define: true,
     require: true,