diff --git a/CHANGELOG-WIP.md b/CHANGELOG-WIP.md
index 7b475113af5..4c9a6a71e76 100644
--- a/CHANGELOG-WIP.md
+++ b/CHANGELOG-WIP.md
@@ -316,6 +316,7 @@
 - `craft\services\Users::unshunMessageForUser()` now has a `void` return type, and throws an `InvalidElementException` in case of failure.
 - `craft\services\Users::unsuspendUser()` now has a `void` return type, and throws an `InvalidElementException` in case of failure.
 - `craft\services\Users::verifyEmailForUser()` now has a `void` return type, and throws an `InvalidElementException` in case of failure.
+- `craft\web\View::setNamespace()` now throws an `InvalidArgumentException` for namespaces that don’t confirm to HTML `id` attribute rules (possibly followed by sets of properly-formatted strings wrapped in square brackets). ([#13943](https://github.com/craftcms/cms/issues/13943))
 - Deprecated the `_elements/element.twig` control panel template. `elementChip()` or `elementCard()` should be used instead.
 - Deprecated the `cp.elements.element` control panel template hook.
 - Deprecated `craft\events\DefineElementInnerHtmlEvent`.
diff --git a/src/web/View.php b/src/web/View.php
index 7ee61e237f4..919a66cf8ab 100644
--- a/src/web/View.php
+++ b/src/web/View.php
@@ -38,6 +38,7 @@
 use Twig\TemplateWrapper;
 use yii\base\Arrayable;
 use yii\base\Exception;
+use yii\base\InvalidArgumentException;
 use yii\base\Model;
 use yii\base\NotSupportedException;
 use yii\web\AssetBundle as YiiAssetBundle;
@@ -1438,6 +1439,13 @@ public function getNamespace(): ?string
      */
     public function setNamespace(?string $namespace): void
     {
+        if (
+            $namespace !== null &&
+            !preg_match('/^[A-Za-z][A-Za-z0-9\-_:.]*(\[[A-Za-z][A-Za-z0-9\-_:.]*])*$/', $namespace)
+        ) {
+            throw new InvalidArgumentException(sprintf('Invalid namespace ("%s"). Namespaces must begin with a letter, and may be followed by letters, numbers, hyphens, underscores, colons, and periods (possibly followed by sets of correctly-formatted strings wrapped in square brackets).', $namespace));
+        }
+
         $this->_namespace = $namespace;
     }
 
diff --git a/tests/unit/web/ViewTest.php b/tests/unit/web/ViewTest.php
index 7c95720f220..d28faf4c918 100644
--- a/tests/unit/web/ViewTest.php
+++ b/tests/unit/web/ViewTest.php
@@ -25,6 +25,7 @@
 use UnitTester;
 use yii\base\Event;
 use yii\base\Exception;
+use yii\base\InvalidArgumentException;
 
 /**
  * Unit tests for the View class
@@ -307,6 +308,26 @@ public function testNamespaceInputId(string $expected, string $string, ?string $
         self::assertSame($expected, $this->view->namespaceInputId($string, $namespace));
     }
 
+    /**
+     * @dataProvider setNamespaceDataProvider
+     * @param string|null $namespace
+     * @param bool $isValid
+     */
+    public function testSetNamespace(?string $namespace, bool $isValid): void
+    {
+        $oldNamespace = $this->view->getNamespace();
+
+        if (!$isValid) {
+            self::expectException(InvalidArgumentException::class);
+        }
+
+        $this->view->setNamespace($namespace);
+        self::assertEquals($namespace, $this->view->getNamespace());
+
+        $this->view->setNamespace($oldNamespace);
+        self::assertEquals($oldNamespace, $this->view->getNamespace());
+    }
+
     /**
      * @dataProvider getTemplateRootsDataProvider
      * @param array $expected
@@ -602,6 +623,31 @@ public static function namespaceInputIdDataProvider(): array
         ];
     }
 
+    /**
+     * @return array
+     */
+    public static function setNamespaceDataProvider(): array
+    {
+        return [
+            [null, true],
+            ['foo', true],
+            ['foo[bar]', true],
+            ['foo[bar][baz]', true],
+            ['foo[bar0:baz.1-_]', true],
+            ['', false],
+            ['0', false],
+            ['1', false],
+            ['foo[]', false],
+            ['foo[0]', false],
+            ['foo[1]', false],
+            ['foo[bar][]', false],
+            ['foo[bar][0]', false],
+            ['foo[bar][1]', false],
+            ['foo[bar', false],
+            [' foo', false],
+        ];
+    }
+
     /**
      * @return array
      */