diff --git a/packages/react-dom-bindings/src/client/ReactDOMComponent.js b/packages/react-dom-bindings/src/client/ReactDOMComponent.js
index 6406b734c439c..15a4ba675b5e0 100644
--- a/packages/react-dom-bindings/src/client/ReactDOMComponent.js
+++ b/packages/react-dom-bindings/src/client/ReactDOMComponent.js
@@ -344,7 +344,7 @@ function setProp(
     case 'children': {
       if (typeof value === 'string') {
         if (__DEV__) {
-          validateTextNesting(value, tag);
+          validateTextNesting(value, tag, false);
         }
         // Avoid setting initial textContent when the text is empty. In IE11 setting
         // textContent on a <textarea> will cause the placeholder to not
@@ -358,7 +358,7 @@ function setProp(
       } else if (typeof value === 'number' || typeof value === 'bigint') {
         if (__DEV__) {
           // $FlowFixMe[unsafe-addition] Flow doesn't want us to use `+` operator with string and bigint
-          validateTextNesting('' + value, tag);
+          validateTextNesting('' + value, tag, false);
         }
         const canSetTextContent = tag !== 'body';
         if (canSetTextContent) {
diff --git a/packages/react-dom-bindings/src/client/ReactFiberConfigDOM.js b/packages/react-dom-bindings/src/client/ReactFiberConfigDOM.js
index c23222879ba8a..93705d2995ebb 100644
--- a/packages/react-dom-bindings/src/client/ReactFiberConfigDOM.js
+++ b/packages/react-dom-bindings/src/client/ReactFiberConfigDOM.js
@@ -594,7 +594,11 @@ export function createTextInstance(
     const hostContextDev = ((hostContext: any): HostContextDev);
     const ancestor = hostContextDev.ancestorInfo.current;
     if (ancestor != null) {
-      validateTextNesting(text, ancestor.tag);
+      validateTextNesting(
+        text,
+        ancestor.tag,
+        hostContextDev.ancestorInfo.implicitRootScope,
+      );
     }
   }
   const textNode: TextInstance = getOwnerDocumentFromRootContainer(
@@ -2027,7 +2031,11 @@ export function validateHydratableTextInstance(
     const hostContextDev = ((hostContext: any): HostContextDev);
     const ancestor = hostContextDev.ancestorInfo.current;
     if (ancestor != null) {
-      return validateTextNesting(text, ancestor.tag);
+      return validateTextNesting(
+        text,
+        ancestor.tag,
+        hostContextDev.ancestorInfo.implicitRootScope,
+      );
     }
   }
   return true;
diff --git a/packages/react-dom-bindings/src/client/validateDOMNesting.js b/packages/react-dom-bindings/src/client/validateDOMNesting.js
index d6fdc5e857ed3..77a416932455e 100644
--- a/packages/react-dom-bindings/src/client/validateDOMNesting.js
+++ b/packages/react-dom-bindings/src/client/validateDOMNesting.js
@@ -71,6 +71,7 @@ export type AncestorInfoDev = {
 
   // <head> or <body>
   containerTagInScope: ?Info,
+  implicitRootScope: boolean,
 };
 
 // This validation code was written based on the HTML5 parsing spec:
@@ -219,10 +220,11 @@ const emptyAncestorInfoDev: AncestorInfoDev = {
   dlItemTagAutoclosing: null,
 
   containerTagInScope: null,
+  implicitRootScope: false,
 };
 
 function updatedAncestorInfoDev(
-  oldInfo: ?AncestorInfoDev,
+  oldInfo: null | AncestorInfoDev,
   tag: string,
 ): AncestorInfoDev {
   if (__DEV__) {
@@ -238,14 +240,14 @@ function updatedAncestorInfoDev(
       ancestorInfo.pTagInButtonScope = null;
     }
 
-    // See rules for 'li', 'dd', 'dt' start tags in
-    // https://html.spec.whatwg.org/multipage/syntax.html#parsing-main-inbody
     if (
       specialTags.indexOf(tag) !== -1 &&
       tag !== 'address' &&
       tag !== 'div' &&
       tag !== 'p'
     ) {
+      // See rules for 'li', 'dd', 'dt' start tags in
+      // https://html.spec.whatwg.org/multipage/syntax.html#parsing-main-inbody
       ancestorInfo.listItemTagAutoclosing = null;
       ancestorInfo.dlItemTagAutoclosing = null;
     }
@@ -279,6 +281,17 @@ function updatedAncestorInfoDev(
       ancestorInfo.containerTagInScope = info;
     }
 
+    if (
+      oldInfo === null &&
+      (tag === '#document' || tag === 'html' || tag === 'body')
+    ) {
+      // While <head> is also a singleton we don't want to support semantics where
+      // you can escape the head by rendering a body singleton so we treat it like a normal scope
+      ancestorInfo.implicitRootScope = true;
+    } else if (ancestorInfo.implicitRootScope === true) {
+      ancestorInfo.implicitRootScope = false;
+    }
+
     return ancestorInfo;
   } else {
     return (null: any);
@@ -288,7 +301,11 @@ function updatedAncestorInfoDev(
 /**
  * Returns whether
  */
-function isTagValidWithParent(tag: string, parentTag: ?string): boolean {
+function isTagValidWithParent(
+  tag: string,
+  parentTag: ?string,
+  implicitRootScope: boolean,
+): boolean {
   // First, let's check if we're in an unusual parsing mode...
   switch (parentTag) {
     // https://html.spec.whatwg.org/multipage/syntax.html#parsing-main-inselect
@@ -363,10 +380,16 @@ function isTagValidWithParent(tag: string, parentTag: ?string): boolean {
       );
     // https://html.spec.whatwg.org/multipage/semantics.html#the-html-element
     case 'html':
+      if (implicitRootScope) {
+        break;
+      }
       return tag === 'head' || tag === 'body' || tag === 'frameset';
     case 'frameset':
       return tag === 'frame';
     case '#document':
+      if (implicitRootScope) {
+        break;
+      }
       return tag === 'html';
   }
 
@@ -393,14 +416,11 @@ function isTagValidWithParent(tag: string, parentTag: ?string): boolean {
     case 'rt':
       return impliedEndTags.indexOf(parentTag) === -1;
 
-    case 'body':
     case 'caption':
     case 'col':
     case 'colgroup':
     case 'frameset':
     case 'frame':
-    case 'head':
-    case 'html':
     case 'tbody':
     case 'td':
     case 'tfoot':
@@ -412,6 +432,21 @@ function isTagValidWithParent(tag: string, parentTag: ?string): boolean {
       // so we allow it only if we don't know what the parent is, as all other
       // cases are invalid.
       return parentTag == null;
+    case 'head':
+      return (implicitRootScope && parentTag !== 'head') || parentTag === null;
+    case 'html':
+      return (
+        (implicitRootScope &&
+          parentTag !== 'body' &&
+          parentTag !== 'html' &&
+          parentTag !== 'head') ||
+        parentTag === null
+      );
+    case 'body':
+      return (
+        (implicitRootScope && parentTag !== 'body' && parentTag !== 'head') ||
+        parentTag === null
+      );
   }
 
   return true;
@@ -513,7 +548,11 @@ function validateDOMNesting(
     const parentInfo = ancestorInfo.current;
     const parentTag = parentInfo && parentInfo.tag;
 
-    const invalidParent = isTagValidWithParent(childTag, parentTag)
+    const invalidParent = isTagValidWithParent(
+      childTag,
+      parentTag,
+      ancestorInfo.implicitRootScope,
+    )
       ? null
       : parentInfo;
     const invalidAncestor = invalidParent
@@ -594,9 +633,13 @@ function validateDOMNesting(
   return true;
 }
 
-function validateTextNesting(childText: string, parentTag: string): boolean {
+function validateTextNesting(
+  childText: string,
+  parentTag: string,
+  implicitRootScope: boolean,
+): boolean {
   if (__DEV__) {
-    if (isTagValidWithParent('#text', parentTag)) {
+    if (implicitRootScope || isTagValidWithParent('#text', parentTag, false)) {
       return true;
     }
 
diff --git a/packages/react-dom/src/__tests__/ReactDOM-test.js b/packages/react-dom/src/__tests__/ReactDOM-test.js
index ef0dd50258122..0d4a758a3c298 100644
--- a/packages/react-dom/src/__tests__/ReactDOM-test.js
+++ b/packages/react-dom/src/__tests__/ReactDOM-test.js
@@ -601,10 +601,6 @@ describe('ReactDOM', () => {
       '<html lang="en"><head data-h=""><meta itemprop="" content="head"></head><body data-b=""><div>before</div><div>inside</div><div>after</div></body></html>',
     );
 
-    // @TODO remove this warning check when we loosen the tag nesting restrictions to allow arbitrary tags at the
-    // root of the application
-    assertConsoleErrorDev(['In HTML, <div> cannot be a child of <#document>']);
-
     await act(() => {
       root.render(<App phase={1} />);
     });
@@ -666,10 +662,6 @@ describe('ReactDOM', () => {
       '<html><head data-h=""><meta itemprop="" content="head"></head><body data-b=""><div>before</div><div>inside</div><div>after</div></body></html>',
     );
 
-    // @TODO remove this warning check when we loosen the tag nesting restrictions to allow arbitrary tags at the
-    // root of the application
-    assertConsoleErrorDev(['In HTML, <div> cannot be a child of <html>']);
-
     await act(() => {
       root.render(<App phase={1} />);
     });
@@ -729,10 +721,6 @@ describe('ReactDOM', () => {
       '<html><head data-h=""><meta itemprop="" content="head"></head><body><div>before</div><div>inside</div><div>after</div></body></html>',
     );
 
-    // @TODO remove this warning check when we loosen the tag nesting restrictions to allow arbitrary tags at the
-    // root of the application
-    assertConsoleErrorDev(['In HTML, <head> cannot be a child of <body>']);
-
     await act(() => {
       root.render(<App phase={1} />);
     });
diff --git a/packages/react-dom/src/__tests__/ReactDOMFizzServer-test.js b/packages/react-dom/src/__tests__/ReactDOMFizzServer-test.js
index d0a1e484f2810..d64167015eec9 100644
--- a/packages/react-dom/src/__tests__/ReactDOMFizzServer-test.js
+++ b/packages/react-dom/src/__tests__/ReactDOMFizzServer-test.js
@@ -9004,7 +9004,6 @@ describe('ReactDOMFizzServer', () => {
         </body>
       </html>,
     );
-    assertConsoleErrorDev(['In HTML, <div> cannot be a child of <#document>']);
 
     root.unmount();
     expect(getVisibleChildren(document)).toEqual(
@@ -10173,7 +10172,6 @@ describe('ReactDOMFizzServer', () => {
         </body>
       </html>,
     );
-    assertConsoleErrorDev(['In HTML, <div> cannot be a child of <#document>']);
 
     root.unmount();
     expect(getVisibleChildren(document)).toEqual(
diff --git a/packages/react-dom/src/__tests__/ReactDOMFloat-test.js b/packages/react-dom/src/__tests__/ReactDOMFloat-test.js
index bdd50c9d4f469..4375ddb7d8deb 100644
--- a/packages/react-dom/src/__tests__/ReactDOMFloat-test.js
+++ b/packages/react-dom/src/__tests__/ReactDOMFloat-test.js
@@ -511,9 +511,6 @@ describe('ReactDOMFloat', () => {
         'Cannot render <noscript> outside the main document. Try moving it into the root <head> tag.',
         {withoutStack: true},
       ],
-      'In HTML, <noscript> cannot be a child of <#document>.\n' +
-        'This will cause a hydration error.\n' +
-        '    in noscript (at **)',
     ]);
 
     root.render(
@@ -577,9 +574,6 @@ describe('ReactDOMFloat', () => {
           'Consider adding precedence="default" or moving it into the root <head> tag.',
         {withoutStack: true},
       ],
-      'In HTML, <link> cannot be a child of <#document>.\n' +
-        'This will cause a hydration error.\n' +
-        '    in link (at **)',
     ]);
 
     root.render(
diff --git a/packages/react-dom/src/__tests__/validateDOMNesting-test.js b/packages/react-dom/src/__tests__/validateDOMNesting-test.js
index fc4fb0f80d44a..38bf4258bac4f 100644
--- a/packages/react-dom/src/__tests__/validateDOMNesting-test.js
+++ b/packages/react-dom/src/__tests__/validateDOMNesting-test.js
@@ -19,28 +19,54 @@ function expectWarnings(tags, warnings = [], withoutStack = 0) {
   tags = [...tags];
   warnings = [...warnings];
 
+  document.removeChild(document.documentElement);
+  document.appendChild(document.createElement('html'));
+  document.documentElement.innerHTML = '<head></head><body></body>';
+
   let element = null;
   const containerTag = tags.shift();
-  const container =
-    containerTag === 'svg'
-      ? document.createElementNS('http://www.w3.org/2000/svg', containerTag)
-      : document.createElement(containerTag);
+  let container;
+  switch (containerTag) {
+    case '#document':
+      container = document;
+      break;
+    case 'html':
+      container = document.documentElement;
+      break;
+    case 'body':
+      container = document.body;
+      break;
+    case 'head':
+      container = document.head;
+      break;
+    case 'svg':
+      container = document.createElementNS('http://www.w3.org/2000/svg', 'svg');
+      break;
+    default:
+      container = document.createElement(containerTag);
+      break;
+  }
 
   while (tags.length) {
     const Tag = tags.pop();
-    element = <Tag>{element}</Tag>;
+    if (Tag === '#text') {
+      element = 'text';
+    } else {
+      element = <Tag>{element}</Tag>;
+    }
   }
 
   const root = ReactDOMClient.createRoot(container);
+  ReactDOM.flushSync(() => {
+    root.render(element);
+  });
   if (warnings.length) {
-    ReactDOM.flushSync(() => {
-      root.render(element);
-    });
     assertConsoleErrorDev(
       warnings,
       withoutStack > 0 ? {withoutStack} : undefined,
     );
   }
+  root.unmount();
 }
 
 describe('validateDOMNesting', () => {
@@ -138,6 +164,49 @@ describe('validateDOMNesting', () => {
         'In HTML, <body> cannot be a child of <body>.\n' +
           'This will cause a hydration error.\n' +
           '    in body (at **)',
+        'You are mounting a new body component when a previous one has not first unmounted.',
+      ],
+    );
+    expectWarnings(
+      ['head', 'body'],
+      [
+        'In HTML, <body> cannot be a child of <head>.\n' +
+          'This will cause a hydration error.\n' +
+          '    in body (at **)',
+      ],
+    );
+    expectWarnings(
+      ['head', 'head'],
+      [
+        'In HTML, <head> cannot be a child of <head>.\n' +
+          'This will cause a hydration error.\n' +
+          '    in head (at **)',
+        'You are mounting a new head component when a previous one has not first unmounted.',
+      ],
+    );
+    expectWarnings(
+      ['html', 'html'],
+      [
+        'In HTML, <html> cannot be a child of <html>.\n' +
+          'This will cause a hydration error.\n' +
+          '    in html (at **)',
+        'You are mounting a new html component when a previous one has not first unmounted.',
+      ],
+    );
+    expectWarnings(
+      ['body', 'html'],
+      [
+        'In HTML, <html> cannot be a child of <body>.\n' +
+          'This will cause a hydration error.\n' +
+          '    in html (at **)',
+      ],
+    );
+    expectWarnings(
+      ['head', 'html'],
+      [
+        'In HTML, <html> cannot be a child of <head>.\n' +
+          'This will cause a hydration error.\n' +
+          '    in html (at **)',
       ],
     );
     expectWarnings(
@@ -152,8 +221,6 @@ describe('validateDOMNesting', () => {
               '>   <body>\n' +
               '\n' +
               '    in body (at **)',
-            'You are mounting a new body component when a previous one has not first unmounted. It is an error to render more than one body component at a time and attributes and children of these components will likely fail in unpredictable ways. Please only render a single instance of <body> and if you need to mount a new one, ensure any previous ones have unmounted first.\n' +
-              '    in body (at **)',
           ]
         : [
             // TODO, this should say "In SVG",
@@ -171,4 +238,22 @@ describe('validateDOMNesting', () => {
           ],
     );
   });
+
+  it('relaxes the nesting rules at the root when the container is a singleton', () => {
+    expectWarnings(['#document', 'html']);
+    expectWarnings(['#document', 'body']);
+    expectWarnings(['#document', 'head']);
+    expectWarnings(['#document', 'div']);
+    expectWarnings(['#document', 'meta']);
+    expectWarnings(['#document', '#text']);
+    expectWarnings(['html', 'body']);
+    expectWarnings(['html', 'head']);
+    expectWarnings(['html', 'div']);
+    expectWarnings(['html', 'meta']);
+    expectWarnings(['html', '#text']);
+    expectWarnings(['body', 'head']);
+    expectWarnings(['body', 'div']);
+    expectWarnings(['body', 'meta']);
+    expectWarnings(['body', '#text']);
+  });
 });
