diff --git a/docs/README.md b/docs/README.md
index 78b936d8..eb5edc67 100644
--- a/docs/README.md
+++ b/docs/README.md
@@ -69,6 +69,11 @@ import ReactModal from 'react-modal';
      See the `Styles` section for more details.
   */
   bodyOpenClassName="ReactModal__Body--open"
+  /*
+     String className to be applied to the document.html (must be a constant string).
+     See the `Styles` section for more details.
+  */
+  htmlOpenClassName="ReactModal__Html--open"
   /*
     Boolean indicating if the appElement should be hidden
   */
diff --git a/examples/basic/app.css b/examples/basic/app.css
index 6bcc1092..a83abb6e 100644
--- a/examples/basic/app.css
+++ b/examples/basic/app.css
@@ -29,3 +29,8 @@
   transform: scale(0.5) rotateX(30deg);
   transition: all 150ms ease-in;
 }
+
+.ReactModal__Body--open,
+.ReactModal__Html--open {
+  overflow: hidden;
+}
diff --git a/specs/Modal.spec.js b/specs/Modal.spec.js
index d86624fd..54539c6f 100644
--- a/specs/Modal.spec.js
+++ b/specs/Modal.spec.js
@@ -6,6 +6,7 @@ import Modal from "react-modal";
 import * as ariaAppHider from "react-modal/helpers/ariaAppHider";
 import {
   isBodyWithReactModalOpenClass,
+  isHtmlWithReactModalOpenClass,
   contentAttribute,
   mcontent,
   moverlay,
@@ -253,32 +254,49 @@ export default () => {
     (document.body.className.indexOf("custom-modal-open") > -1).should.be.ok();
   });
 
-  it("don't append class to document.body if modal is not open", () => {
+  it("supports overriding react modal open class in html.", () => {
+    renderModal({ isOpen: true, htmlOpenClassName: "custom-modal-open" });
+    (
+      document
+        .getElementsByTagName("html")[0]
+        .className.indexOf("custom-modal-open") > -1
+    ).should.be.ok();
+  });
+
+  // eslint-disable-next-line max-len
+  it("don't append class to document.body and html if modal is not open", () => {
     renderModal({ isOpen: false });
     isBodyWithReactModalOpenClass().should.not.be.ok();
+    isHtmlWithReactModalOpenClass().should.not.be.ok();
     unmountModal();
   });
 
-  it("append class to document.body if modal is open", () => {
+  it("append class to document.body and html if modal is open", () => {
     renderModal({ isOpen: true });
     isBodyWithReactModalOpenClass().should.be.ok();
+    isHtmlWithReactModalOpenClass().should.be.ok();
     unmountModal();
   });
 
-  it("removes class from document.body when unmounted without closing", () => {
+  // eslint-disable-next-line max-len
+  it("removes class from document.body and html when unmounted without closing", () => {
     renderModal({ isOpen: true });
     unmountModal();
     isBodyWithReactModalOpenClass().should.not.be.ok();
+    isHtmlWithReactModalOpenClass().should.not.be.ok();
   });
 
-  it("remove class from document.body when no modals opened", () => {
+  it("remove class from document.body and html when no modals opened", () => {
     renderModal({ isOpen: true });
     renderModal({ isOpen: true });
     isBodyWithReactModalOpenClass().should.be.ok();
+    isHtmlWithReactModalOpenClass().should.be.ok();
     unmountModal();
     isBodyWithReactModalOpenClass().should.be.ok();
+    isHtmlWithReactModalOpenClass().should.be.ok();
     unmountModal();
     isBodyWithReactModalOpenClass().should.not.be.ok();
+    isHtmlWithReactModalOpenClass().should.not.be.ok();
   });
 
   it("supports adding/removing multiple document.body classes", () => {
@@ -328,6 +346,59 @@ export default () => {
     isBodyWithReactModalOpenClass().should.be.ok();
   });
 
+  it("supports adding/removing multiple html classes", () => {
+    renderModal({
+      isOpen: true,
+      htmlOpenClassName: "A B C"
+    });
+    document
+      .getElementsByTagName("html")[0]
+      .classList.contains("A", "B", "C")
+      .should.be.ok();
+    unmountModal();
+    document
+      .getElementsByTagName("html")[0]
+      .classList.contains("A", "B", "C")
+      .should.not.be.ok();
+  });
+
+  it("does not remove shared classes if more than one modal is open", () => {
+    renderModal({
+      isOpen: true,
+      htmlOpenClassName: "A"
+    });
+    renderModal({
+      isOpen: true,
+      htmlOpenClassName: "A B"
+    });
+
+    isHtmlWithReactModalOpenClass("A B").should.be.ok();
+    unmountModal();
+    isHtmlWithReactModalOpenClass("A B").should.not.be.ok();
+    isHtmlWithReactModalOpenClass("A").should.be.ok();
+    unmountModal();
+    isHtmlWithReactModalOpenClass("A").should.not.be.ok();
+  });
+
+  it("should not add classes to html for unopened modals", () => {
+    renderModal({ isOpen: true });
+    isHtmlWithReactModalOpenClass().should.be.ok();
+    renderModal({ isOpen: false, htmlOpenClassName: "testHtmlClass" });
+    isHtmlWithReactModalOpenClass("testHtmlClass").should.not.be.ok();
+  });
+
+  it("should not remove classes from html if modal is closed", () => {
+    renderModal({ isOpen: true });
+    isHtmlWithReactModalOpenClass().should.be.ok();
+    renderModal({ isOpen: false, htmlOpenClassName: "testHtmlClass" });
+    renderModal({ isOpen: false });
+    isHtmlWithReactModalOpenClass("testHtmlClass").should.not.be.ok();
+    isHtmlWithReactModalOpenClass().should.be.ok();
+    renderModal({ isOpen: false });
+    renderModal({ isOpen: false });
+    isHtmlWithReactModalOpenClass().should.be.ok();
+  });
+
   it("additional aria attributes", () => {
     const modal = renderModal(
       { isOpen: true, aria: { labelledby: "a" } },
diff --git a/specs/helper.js b/specs/helper.js
index 1cf57516..c45e06a0 100644
--- a/specs/helper.js
+++ b/specs/helper.js
@@ -1,6 +1,9 @@
 import React from "react";
 import ReactDOM from "react-dom";
-import Modal, { bodyOpenClassName } from "../src/components/Modal";
+import Modal, {
+  bodyOpenClassName,
+  htmlOpenClassName
+} from "../src/components/Modal";
 import TestUtils from "react-dom/test-utils";
 
 const divStack = [];
@@ -30,6 +33,14 @@ if (!String.prototype.includes) {
 export const isBodyWithReactModalOpenClass = (bodyClass = bodyOpenClassName) =>
   document.body.className.includes(bodyClass);
 
+/**
+ * Check if the html contains the react modal
+ * open class.
+ * @return {Boolean}
+ */
+export const isHtmlWithReactModalOpenClass = (htmlClass = htmlOpenClassName) =>
+  document.getElementsByTagName("html")[0].className.includes(htmlClass);
+
 /**
  * Returns a rendered dom element by class.
  * @param {React} element A react instance.
diff --git a/src/components/Modal.js b/src/components/Modal.js
index 7db54386..6b30796c 100644
--- a/src/components/Modal.js
+++ b/src/components/Modal.js
@@ -7,6 +7,7 @@ import SafeHTMLElement, { canUseDOM } from "../helpers/safeHTMLElement";
 
 export const portalClassName = "ReactModalPortal";
 export const bodyOpenClassName = "ReactModal__Body--open";
+export const htmlOpenClassName = "ReactModal__Html--open";
 
 const isReact16 = ReactDOM.createPortal !== undefined;
 const createPortal = isReact16
@@ -31,6 +32,7 @@ export default class Modal extends Component {
     }),
     portalClassName: PropTypes.string,
     bodyOpenClassName: PropTypes.string,
+    htmlOpenClassName: PropTypes.string,
     className: PropTypes.oneOfType([
       PropTypes.string,
       PropTypes.shape({
@@ -69,6 +71,7 @@ export default class Modal extends Component {
     isOpen: false,
     portalClassName,
     bodyOpenClassName,
+    htmlOpenClassName,
     ariaHideApp: true,
     closeTimeoutMS: 0,
     shouldFocusAfterRender: true,
diff --git a/src/components/ModalPortal.js b/src/components/ModalPortal.js
index 5ded7a16..ff47a536 100644
--- a/src/components/ModalPortal.js
+++ b/src/components/ModalPortal.js
@@ -38,6 +38,7 @@ export default class ModalPortal extends Component {
     className: PropTypes.oneOfType([PropTypes.string, PropTypes.object]),
     overlayClassName: PropTypes.oneOfType([PropTypes.string, PropTypes.object]),
     bodyOpenClassName: PropTypes.string,
+    htmlOpenClassName: PropTypes.string,
     ariaHideApp: PropTypes.bool,
     appElement: PropTypes.instanceOf(SafeHTMLElement),
     onAfterOpen: PropTypes.func,
@@ -84,6 +85,13 @@ export default class ModalPortal extends Component {
             "This may cause unexpected behavior when multiple modals are open."
         );
       }
+      if (newProps.htmlOpenClassName !== this.props.htmlOpenClassName) {
+        // eslint-disable-next-line no-console
+        console.warn(
+          'React-Modal: "htmlOpenClassName" prop has been modified. ' +
+            "This may cause unexpected behavior when multiple modals are open."
+        );
+      }
     }
     // Focus only needs to be set once when the modal is being opened
     if (!this.props.isOpen && newProps.isOpen) {
@@ -121,9 +129,15 @@ export default class ModalPortal extends Component {
   };
 
   beforeOpen() {
-    const { appElement, ariaHideApp, bodyOpenClassName } = this.props;
-    // Add body class
-    bodyClassList.add(bodyOpenClassName);
+    const {
+      appElement,
+      ariaHideApp,
+      bodyOpenClassName,
+      htmlOpenClassName
+    } = this.props;
+    // Add body and html class
+    bodyClassList.add(document.body, bodyOpenClassName);
+    classList.add(document.getElementsByTagName("html")[0], htmlOpenClassName);
     // Add aria-hidden to appElement
     if (ariaHideApp) {
       ariaHiddenInstances += 1;
@@ -136,6 +150,10 @@ export default class ModalPortal extends Component {
 
     // Remove body class
     bodyClassList.remove(this.props.bodyOpenClassName);
+    classList.remove(
+      document.getElementsByTagName("html")[0],
+      this.props.htmlOpenClassName
+    );
 
     // Reset aria-hidden attribute if all modals have been removed
     if (ariaHideApp && ariaHiddenInstances > 0) {
diff --git a/src/helpers/bodyClassList.js b/src/helpers/classList.js
similarity index 100%
rename from src/helpers/bodyClassList.js
rename to src/helpers/classList.js