diff --git a/src/Symfony/Component/CssSelector/CHANGELOG.md b/src/Symfony/Component/CssSelector/CHANGELOG.md
index c035d6b3db49e..1c8c6cf76cdce 100644
--- a/src/Symfony/Component/CssSelector/CHANGELOG.md
+++ b/src/Symfony/Component/CssSelector/CHANGELOG.md
@@ -1,8 +1,14 @@
 CHANGELOG
 =========
 
+7.1
+---
+
+* Add support for `:is()`
+* Add support for `:where()`
+
 6.3
------
+---
 
  * Add support for `:scope`
 
diff --git a/src/Symfony/Component/CssSelector/Node/MatchingNode.php b/src/Symfony/Component/CssSelector/Node/MatchingNode.php
new file mode 100644
index 0000000000000..381ac4585d03a
--- /dev/null
+++ b/src/Symfony/Component/CssSelector/Node/MatchingNode.php
@@ -0,0 +1,55 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\CssSelector\Node;
+
+/**
+ * Represents a "<selector>:is(<subSelectorList>)" node.
+ *
+ * This component is a port of the Python cssselect library,
+ * which is copyright Ian Bicking, @see https://github.com/SimonSapin/cssselect.
+ *
+ * @author Hubert Lenoir <lenoir.hubert@gmail.com>
+ *
+ * @internal
+ */
+class MatchingNode extends AbstractNode
+{
+    /**
+     * @param array<NodeInterface> $arguments
+     */
+    public function __construct(
+        public readonly NodeInterface $selector,
+        public readonly array $arguments = [],
+    ) {
+    }
+
+    public function getSpecificity(): Specificity
+    {
+        $argumentsSpecificity = array_reduce(
+            $this->arguments,
+            fn ($c, $n) => 1 === $n->getSpecificity()->compareTo($c) ? $n->getSpecificity() : $c,
+            new Specificity(0, 0, 0),
+        );
+
+        return $this->selector->getSpecificity()->plus($argumentsSpecificity);
+    }
+
+    public function __toString(): string
+    {
+        $selectorArguments = array_map(
+            fn ($n): string => ltrim((string) $n, '*'),
+            $this->arguments,
+        );
+
+        return sprintf('%s[%s:is(%s)]', $this->getNodeName(), $this->selector, implode(', ', $selectorArguments));
+    }
+}
diff --git a/src/Symfony/Component/CssSelector/Node/SpecificityAdjustmentNode.php b/src/Symfony/Component/CssSelector/Node/SpecificityAdjustmentNode.php
new file mode 100644
index 0000000000000..d49ed4c5f90e6
--- /dev/null
+++ b/src/Symfony/Component/CssSelector/Node/SpecificityAdjustmentNode.php
@@ -0,0 +1,49 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\CssSelector\Node;
+
+/**
+ * Represents a "<selector>:where(<subSelectorList>)" node.
+ *
+ * This component is a port of the Python cssselect library,
+ * which is copyright Ian Bicking, @see https://github.com/SimonSapin/cssselect.
+ *
+ * @author Hubert Lenoir <lenoir.hubert@gmail.com>
+ *
+ * @internal
+ */
+class SpecificityAdjustmentNode extends AbstractNode
+{
+    /**
+     * @param array<NodeInterface> $arguments
+     */
+    public function __construct(
+        public readonly NodeInterface $selector,
+        public readonly array $arguments = [],
+    ) {
+    }
+
+    public function getSpecificity(): Specificity
+    {
+        return $this->selector->getSpecificity();
+    }
+
+    public function __toString(): string
+    {
+        $selectorArguments = array_map(
+            fn ($n) => ltrim((string) $n, '*'),
+            $this->arguments,
+        );
+
+        return sprintf('%s[%s:where(%s)]', $this->getNodeName(), $this->selector, implode(', ', $selectorArguments));
+    }
+}
diff --git a/src/Symfony/Component/CssSelector/Parser/Parser.php b/src/Symfony/Component/CssSelector/Parser/Parser.php
index 5313d3435ba9c..462714c8b24a7 100644
--- a/src/Symfony/Component/CssSelector/Parser/Parser.php
+++ b/src/Symfony/Component/CssSelector/Parser/Parser.php
@@ -87,13 +87,17 @@ public static function parseSeries(array $tokens): array
         ];
     }
 
-    private function parseSelectorList(TokenStream $stream): array
+    private function parseSelectorList(TokenStream $stream, bool $isArgument = false): array
     {
         $stream->skipWhitespace();
         $selectors = [];
 
         while (true) {
-            $selectors[] = $this->parserSelectorNode($stream);
+            if ($isArgument && $stream->getPeek()->isDelimiter([')'])) {
+                break;
+            }
+
+            $selectors[] = $this->parserSelectorNode($stream, $isArgument);
 
             if ($stream->getPeek()->isDelimiter([','])) {
                 $stream->getNext();
@@ -106,15 +110,19 @@ private function parseSelectorList(TokenStream $stream): array
         return $selectors;
     }
 
-    private function parserSelectorNode(TokenStream $stream): Node\SelectorNode
+    private function parserSelectorNode(TokenStream $stream, bool $isArgument = false): Node\SelectorNode
     {
-        [$result, $pseudoElement] = $this->parseSimpleSelector($stream);
+        [$result, $pseudoElement] = $this->parseSimpleSelector($stream, false, $isArgument);
 
         while (true) {
             $stream->skipWhitespace();
             $peek = $stream->getPeek();
 
-            if ($peek->isFileEnd() || $peek->isDelimiter([','])) {
+            if (
+                $peek->isFileEnd()
+                || $peek->isDelimiter([','])
+                || ($isArgument && $peek->isDelimiter([')']))
+            ) {
                 break;
             }
 
@@ -129,7 +137,7 @@ private function parserSelectorNode(TokenStream $stream): Node\SelectorNode
                 $combinator = ' ';
             }
 
-            [$nextSelector, $pseudoElement] = $this->parseSimpleSelector($stream);
+            [$nextSelector, $pseudoElement] = $this->parseSimpleSelector($stream, false, $isArgument);
             $result = new Node\CombinedSelectorNode($result, $combinator, $nextSelector);
         }
 
@@ -141,7 +149,7 @@ private function parserSelectorNode(TokenStream $stream): Node\SelectorNode
      *
      * @throws SyntaxErrorException
      */
-    private function parseSimpleSelector(TokenStream $stream, bool $insideNegation = false): array
+    private function parseSimpleSelector(TokenStream $stream, bool $insideNegation = false, bool $isArgument = false): array
     {
         $stream->skipWhitespace();
 
@@ -154,7 +162,7 @@ private function parseSimpleSelector(TokenStream $stream, bool $insideNegation =
             if ($peek->isWhitespace()
                 || $peek->isFileEnd()
                 || $peek->isDelimiter([',', '+', '>', '~'])
-                || ($insideNegation && $peek->isDelimiter([')']))
+                || ($isArgument && $peek->isDelimiter([')']))
             ) {
                 break;
             }
@@ -215,7 +223,7 @@ private function parseSimpleSelector(TokenStream $stream, bool $insideNegation =
                         throw SyntaxErrorException::nestedNot();
                     }
 
-                    [$argument, $argumentPseudoElement] = $this->parseSimpleSelector($stream, true);
+                    [$argument, $argumentPseudoElement] = $this->parseSimpleSelector($stream, true, true);
                     $next = $stream->getNext();
 
                     if (null !== $argumentPseudoElement) {
@@ -227,6 +235,24 @@ private function parseSimpleSelector(TokenStream $stream, bool $insideNegation =
                     }
 
                     $result = new Node\NegationNode($result, $argument);
+                } elseif ('is' === strtolower($identifier)) {
+                    $selectors = $this->parseSelectorList($stream, true);
+
+                    $next = $stream->getNext();
+                    if (!$next->isDelimiter([')'])) {
+                        throw SyntaxErrorException::unexpectedToken('")"', $next);
+                    }
+
+                    $result = new Node\MatchingNode($result, $selectors);
+                } elseif ('where' === strtolower($identifier)) {
+                    $selectors = $this->parseSelectorList($stream, true);
+
+                    $next = $stream->getNext();
+                    if (!$next->isDelimiter([')'])) {
+                        throw SyntaxErrorException::unexpectedToken('")"', $next);
+                    }
+
+                    $result = new Node\SpecificityAdjustmentNode($result, $selectors);
                 } else {
                     $arguments = [];
                     $next = null;
diff --git a/src/Symfony/Component/CssSelector/Tests/Node/MatchingNodeTest.php b/src/Symfony/Component/CssSelector/Tests/Node/MatchingNodeTest.php
new file mode 100644
index 0000000000000..0bc718c4c6d49
--- /dev/null
+++ b/src/Symfony/Component/CssSelector/Tests/Node/MatchingNodeTest.php
@@ -0,0 +1,48 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\CssSelector\Tests\Node;
+
+use Symfony\Component\CssSelector\Node\ClassNode;
+use Symfony\Component\CssSelector\Node\ElementNode;
+use Symfony\Component\CssSelector\Node\HashNode;
+use Symfony\Component\CssSelector\Node\MatchingNode;
+
+class MatchingNodeTest extends AbstractNodeTestCase
+{
+    public static function getToStringConversionTestData()
+    {
+        return [
+            [new MatchingNode(new ElementNode(), [
+                new ClassNode(new ElementNode(), 'class'),
+                new HashNode(new ElementNode(), 'id'),
+            ]), 'Matching[Element[*]:is(Class[Element[*].class], Hash[Element[*]#id])]'],
+        ];
+    }
+
+    public static function getSpecificityValueTestData()
+    {
+        return [
+            [new MatchingNode(new ElementNode(), [
+                new ClassNode(new ElementNode(), 'class'),
+                new HashNode(new ElementNode(), 'id'),
+            ]), 100],
+            [new MatchingNode(new ClassNode(new ElementNode(), 'class'), [
+                new ClassNode(new ElementNode(), 'class'),
+                new HashNode(new ElementNode(), 'id'),
+            ]), 110],
+            [new MatchingNode(new HashNode(new ElementNode(), 'id'), [
+                new ClassNode(new ElementNode(), 'class'),
+                new HashNode(new ElementNode(), 'id'),
+            ]), 200],
+        ];
+    }
+}
diff --git a/src/Symfony/Component/CssSelector/Tests/Node/SpecificityAdjustmentNodeTest.php b/src/Symfony/Component/CssSelector/Tests/Node/SpecificityAdjustmentNodeTest.php
new file mode 100644
index 0000000000000..5c830571e5437
--- /dev/null
+++ b/src/Symfony/Component/CssSelector/Tests/Node/SpecificityAdjustmentNodeTest.php
@@ -0,0 +1,44 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\CssSelector\Tests\Node;
+
+use Symfony\Component\CssSelector\Node\ClassNode;
+use Symfony\Component\CssSelector\Node\ElementNode;
+use Symfony\Component\CssSelector\Node\HashNode;
+use Symfony\Component\CssSelector\Node\SpecificityAdjustmentNode;
+
+class SpecificityAdjustmentNodeTest extends AbstractNodeTestCase
+{
+    public static function getToStringConversionTestData()
+    {
+        return [
+            [new SpecificityAdjustmentNode(new ElementNode(), [
+                new ClassNode(new ElementNode(), 'class'),
+                new HashNode(new ElementNode(), 'id'),
+            ]), 'SpecificityAdjustment[Element[*]:where(Class[Element[*].class], Hash[Element[*]#id])]'],
+        ];
+    }
+
+    public static function getSpecificityValueTestData()
+    {
+        return [
+            [new SpecificityAdjustmentNode(new ElementNode(), [
+                new ClassNode(new ElementNode(), 'class'),
+                new HashNode(new ElementNode(), 'id'),
+            ]), 0],
+            [new SpecificityAdjustmentNode(new ClassNode(new ElementNode(), 'class'), [
+                new ClassNode(new ElementNode(), 'class'),
+                new HashNode(new ElementNode(), 'id'),
+            ]), 10],
+        ];
+    }
+}
diff --git a/src/Symfony/Component/CssSelector/Tests/Parser/ParserTest.php b/src/Symfony/Component/CssSelector/Tests/Parser/ParserTest.php
index a8708ce47282e..509f6e35930e9 100644
--- a/src/Symfony/Component/CssSelector/Tests/Parser/ParserTest.php
+++ b/src/Symfony/Component/CssSelector/Tests/Parser/ParserTest.php
@@ -152,6 +152,10 @@ public static function getParserTestData()
             [':scope', ['Pseudo[Element[*]:scope]']],
             ['foo bar, :scope > div', ['CombinedSelector[Element[foo] <followed> Element[bar]]', 'CombinedSelector[Pseudo[Element[*]:scope] > Element[div]]']],
             ['foo bar,:scope > div', ['CombinedSelector[Element[foo] <followed> Element[bar]]', 'CombinedSelector[Pseudo[Element[*]:scope] > Element[div]]']],
+            ['div:is(.foo, #bar)', ['Matching[Element[div]:is(Selector[Class[Element[*].foo]], Selector[Hash[Element[*]#bar]])]']],
+            [':is(:hover, :visited)', ['Matching[Element[*]:is(Selector[Pseudo[Element[*]:hover]], Selector[Pseudo[Element[*]:visited]])]']],
+            ['div:where(.foo, #bar)', ['SpecificityAdjustment[Element[div]:where(Selector[Class[Element[*].foo]], Selector[Hash[Element[*]#bar]])]']],
+            [':where(:hover, :visited)', ['SpecificityAdjustment[Element[*]:where(Selector[Pseudo[Element[*]:hover]], Selector[Pseudo[Element[*]:visited]])]']],
         ];
     }
 
@@ -183,6 +187,7 @@ public static function getParserExceptionTestData()
             [':contains("foo', SyntaxErrorException::unclosedString(10)->getMessage()],
             ['foo!', SyntaxErrorException::unexpectedToken('selector', new Token(Token::TYPE_DELIMITER, '!', 3))->getMessage()],
             [':scope > div :scope header', SyntaxErrorException::notAtTheStartOfASelector('scope')->getMessage()],
+            [':not(:not(a))', SyntaxErrorException::nestedNot()->getMessage()],
         ];
     }
 
@@ -233,6 +238,18 @@ public static function getSpecificityTestData()
             ['foo::before', 2],
             ['foo:empty::before', 12],
             ['#lorem + foo#ipsum:first-child > bar:first-line', 213],
+            [':is(*)', 0],
+            [':is(foo)', 1],
+            [':is(.foo)', 10],
+            [':is(#foo)', 100],
+            [':is(#foo, :empty, foo)', 100],
+            ['#foo:is(#bar:empty)', 210],
+            [':where(*)', 0],
+            [':where(foo)', 0],
+            [':where(.foo)', 0],
+            [':where(#foo)', 0],
+            [':where(#foo, :empty, foo)', 0],
+            ['#foo:where(#bar:empty)', 100],
         ];
     }
 
diff --git a/src/Symfony/Component/CssSelector/Tests/XPath/TranslatorTest.php b/src/Symfony/Component/CssSelector/Tests/XPath/TranslatorTest.php
index bfb90728bee29..55a2b10a7c3e5 100644
--- a/src/Symfony/Component/CssSelector/Tests/XPath/TranslatorTest.php
+++ b/src/Symfony/Component/CssSelector/Tests/XPath/TranslatorTest.php
@@ -221,6 +221,8 @@ public static function getCssToXPathTestData()
             ['div#container p', "div[@id = 'container']/descendant-or-self::*/p"],
             [':scope > div[dataimg="<testmessage>"]', "*[1]/div[@dataimg = '<testmessage>']"],
             [':scope', '*[1]'],
+            ['e:is(section, article) h1', "e[(name() = 'section') or (name() = 'article')]/descendant-or-self::*/h1"],
+            ['e:where(section, article) h1', "e[(name() = 'section') or (name() = 'article')]/descendant-or-self::*/h1"],
         ];
     }
 
@@ -355,6 +357,17 @@ public static function getHtmlIdsTestData()
             [':not(*)', []],
             ['a:not([href])', ['name-anchor']],
             ['ol :Not(li[class])', ['first-li', 'second-li', 'li-div', 'fifth-li', 'sixth-li', 'seventh-li']],
+            [':is(#first-li, #second-li)', ['first-li', 'second-li']],
+            ['a:is(#name-anchor, #tag-anchor)', ['name-anchor', 'tag-anchor']],
+            [':is(.c)', ['first-ol', 'third-li', 'fourth-li']],
+            ['a:is(:not(#name-anchor))', ['tag-anchor', 'nofollow-anchor']],
+            ['a:not(:is(#name-anchor))', ['tag-anchor', 'nofollow-anchor']],
+            [':where(#first-li, #second-li)', ['first-li', 'second-li']],
+            ['a:where(#name-anchor, #tag-anchor)', ['name-anchor', 'tag-anchor']],
+            [':where(.c)', ['first-ol', 'third-li', 'fourth-li']],
+            ['a:where(:not(#name-anchor))', ['tag-anchor', 'nofollow-anchor']],
+            ['a:not(:where(#name-anchor))', ['tag-anchor', 'nofollow-anchor']],
+            ['a:where(:is(#name-anchor), :where(#tag-anchor))', ['name-anchor', 'tag-anchor']],
             // HTML-specific
             [':link', ['link-href', 'tag-anchor', 'nofollow-anchor', 'area-href']],
             [':visited', []],
@@ -416,6 +429,7 @@ public static function getHtmlShakespearTestData()
             [':scope > div', 1],
             [':scope > div > div[class=dialog]', 1],
             [':scope > div div', 242],
+            ['div:is(div#test .dialog) .direction', 4],
         ];
     }
 }
diff --git a/src/Symfony/Component/CssSelector/XPath/Extension/NodeExtension.php b/src/Symfony/Component/CssSelector/XPath/Extension/NodeExtension.php
index 49e894adee0df..174d009c77306 100644
--- a/src/Symfony/Component/CssSelector/XPath/Extension/NodeExtension.php
+++ b/src/Symfony/Component/CssSelector/XPath/Extension/NodeExtension.php
@@ -65,6 +65,8 @@ public function getNodeTranslators(): array
             'Selector' => $this->translateSelector(...),
             'CombinedSelector' => $this->translateCombinedSelector(...),
             'Negation' => $this->translateNegation(...),
+            'Matching' => $this->translateMatching(...),
+            'SpecificityAdjustment' => $this->translateSpecificityAdjustment(...),
             'Function' => $this->translateFunction(...),
             'Pseudo' => $this->translatePseudo(...),
             'Attribute' => $this->translateAttribute(...),
@@ -97,6 +99,36 @@ public function translateNegation(Node\NegationNode $node, Translator $translato
         return $xpath->addCondition('0');
     }
 
+    public function translateMatching(Node\MatchingNode $node, Translator $translator): XPathExpr
+    {
+        $xpath = $translator->nodeToXPath($node->selector);
+
+        foreach ($node->arguments as $argument) {
+            $expr = $translator->nodeToXPath($argument);
+            $expr->addNameTest();
+            if ($condition = $expr->getCondition()) {
+                $xpath->addCondition($condition, 'or');
+            }
+        }
+
+        return $xpath;
+    }
+
+    public function translateSpecificityAdjustment(Node\SpecificityAdjustmentNode $node, Translator $translator): XPathExpr
+    {
+        $xpath = $translator->nodeToXPath($node->selector);
+
+        foreach ($node->arguments as $argument) {
+            $expr = $translator->nodeToXPath($argument);
+            $expr->addNameTest();
+            if ($condition = $expr->getCondition()) {
+                $xpath->addCondition($condition, 'or');
+            }
+        }
+
+        return $xpath;
+    }
+
     public function translateFunction(Node\FunctionNode $node, Translator $translator): XPathExpr
     {
         $xpath = $translator->nodeToXPath($node->getSelector());
diff --git a/src/Symfony/Component/CssSelector/XPath/XPathExpr.php b/src/Symfony/Component/CssSelector/XPath/XPathExpr.php
index a76e30bec37d2..8cde461dc6ff3 100644
--- a/src/Symfony/Component/CssSelector/XPath/XPathExpr.php
+++ b/src/Symfony/Component/CssSelector/XPath/XPathExpr.php
@@ -46,9 +46,9 @@ public function getElement(): string
     /**
      * @return $this
      */
-    public function addCondition(string $condition): static
+    public function addCondition(string $condition, string $operator = 'and'): static
     {
-        $this->condition = $this->condition ? sprintf('(%s) and (%s)', $this->condition, $condition) : $condition;
+        $this->condition = $this->condition ? sprintf('(%s) %s (%s)', $this->condition, $operator, $condition) : $condition;
 
         return $this;
     }