diff --git a/composer.json b/composer.json
index d5d0b149..03dee62d 100644
--- a/composer.json
+++ b/composer.json
@@ -24,7 +24,7 @@
         "silverstripe/versioned": "^3"
     },
     "require-dev": {
-        "phpunit/phpunit": "^9.6",
+        "phpunit/phpunit": "^11.3",
         "squizlabs/php_codesniffer": "^3",
         "silverstripe/standards": "^1",
         "phpstan/extension-installer": "^1.3"
diff --git a/tests/php/FileSubsitesTest.php b/tests/php/FileSubsitesTest.php
index 497bdba4..8dcc5fba 100644
--- a/tests/php/FileSubsitesTest.php
+++ b/tests/php/FileSubsitesTest.php
@@ -10,6 +10,7 @@
 use SilverStripe\Subsites\Model\Subsite;
 use SilverStripe\Security\Member;
 use ReflectionMethod;
+use PHPUnit\Framework\Attributes\DataProvider;
 
 class FileSubsitesTest extends BaseSubsiteTest
 {
@@ -74,9 +75,7 @@ public function testWritingSubsiteID()
         $this->assertEquals($folder->SubsiteID, $file->SubsiteID);
     }
 
-    /**
-     * @dataProvider provideTestCanEdit
-     */
+    #[DataProvider('provideTestCanEdit')]
     public function testCanEdit(
         string $fileKey,
         string $memberKey,
@@ -91,7 +90,7 @@ public function testCanEdit(
         $this->assertSame($expected, $file->canEdit($member));
     }
 
-    public function provideTestCanEdit(): array
+    public static function provideTestCanEdit(): array
     {
         $ret = [];
         $data = [
diff --git a/tests/php/Service/ThemeResolverTest.php b/tests/php/Service/ThemeResolverTest.php
index 7f0fd7e0..67eea1b8 100644
--- a/tests/php/Service/ThemeResolverTest.php
+++ b/tests/php/Service/ThemeResolverTest.php
@@ -7,6 +7,7 @@
 use SilverStripe\Subsites\Model\Subsite;
 use SilverStripe\Subsites\Service\ThemeResolver;
 use SilverStripe\View\SSViewer;
+use PHPUnit\Framework\Attributes\DataProvider;
 
 class ThemeResolverTest extends SapphireTest
 {
@@ -64,9 +65,7 @@ public function testSubsiteWithCustomThemeDoesNotCascadeUpTheList()
         $this->assertSame($expected, $resolver->getThemeList($subsite));
     }
 
-    /**
-     * @dataProvider customThemeDefinitionsAreRespectedProvider
-     */
+    #[DataProvider('customThemeDefinitionsAreRespectedProvider')]
     public function testCustomThemeDefinitionsAreRespected($themeOptions, $siteTheme, $expected)
     {
         Config::modify()->set(ThemeResolver::class, 'theme_options', $themeOptions);
@@ -79,7 +78,7 @@ public function testCustomThemeDefinitionsAreRespected($themeOptions, $siteTheme
         $this->assertSame($expected, $resolver->getThemeList($subsite));
     }
 
-    public function customThemeDefinitionsAreRespectedProvider()
+    public static function customThemeDefinitionsAreRespectedProvider()
     {
         return [
             // Simple
diff --git a/tests/php/SiteTreeSubsitesTest.php b/tests/php/SiteTreeSubsitesTest.php
index b7e59562..adb65115 100644
--- a/tests/php/SiteTreeSubsitesTest.php
+++ b/tests/php/SiteTreeSubsitesTest.php
@@ -26,6 +26,7 @@
 use SilverStripe\Versioned\Versioned;
 use SilverStripe\View\SSViewer;
 use TractorCow\Fluent\Extension\FluentSiteTreeExtension;
+use PHPUnit\Framework\Attributes\DataProvider;
 
 class SiteTreeSubsitesTest extends BaseSubsiteTest
 {
@@ -94,7 +95,7 @@ public function testBasicSanity()
         $this->assertInstanceOf(FieldList::class, singleton(SubsitesVirtualPage::class)->getCMSFields());
     }
 
-    public function errorPageLocationsProvider()
+    public static function errorPageLocationsProvider()
     {
         return [
             ['domaintest1', '/error-500-one.example.org.html'],
@@ -102,9 +103,7 @@ public function errorPageLocationsProvider()
         ];
     }
 
-    /**
-     * @dataProvider errorPageLocationsProvider
-     */
+    #[DataProvider('errorPageLocationsProvider')]
     public function testErrorPageLocations($subsiteFixtureName, $expectedFilename)
     {
         $static_path = Config::inst()->get(ErrorPage::class, 'static_filepath');
@@ -382,8 +381,8 @@ public function testValidateURLSegment()
     /**
      * @param bool $withChildren
      * @param int $expectedChildren
-     * @dataProvider duplicateToSubsiteProvider
      */
+    #[DataProvider('duplicateToSubsiteProvider')]
     public function testDuplicateToSubsite($withChildren, $expectedChildren)
     {
         /** @var SiteTree $page */
@@ -408,7 +407,7 @@ public function testDuplicateToSubsite($withChildren, $expectedChildren)
     /**
      * @return array[]
      */
-    public function duplicateToSubsiteProvider()
+    public static function duplicateToSubsiteProvider()
     {
         return [
             [true, 1],
@@ -437,7 +436,7 @@ public function testThemeResolverIsUsedForSettingThemeList()
         SiteTree::singleton()->extend('contentcontrollerInit', $controller);
     }
 
-    public function provideAlternateAbsoluteLink()
+    public static function provideAlternateAbsoluteLink()
     {
         return [
             ['home', null, 'http://localhost'],
@@ -452,11 +451,11 @@ public function provideAlternateAbsoluteLink()
     }
 
     /**
-     * @dataProvider provideAlternateAbsoluteLink
      * @param string $pageFixtureName
      * @param string|null $action
      * @param string $expectedAbsoluteLink
      */
+    #[DataProvider('provideAlternateAbsoluteLink')]
     public function testAlternateAbsoluteLink($pageFixtureName, $action, $expectedAbsoluteLink)
     {
         // Setting a control value, in case base url is set for the installation under test
diff --git a/tests/php/SubsiteTest.php b/tests/php/SubsiteTest.php
index 74ec6cbe..228c0b49 100644
--- a/tests/php/SubsiteTest.php
+++ b/tests/php/SubsiteTest.php
@@ -13,6 +13,7 @@
 use SilverStripe\Subsites\Model\SubsiteDomain;
 use SilverStripe\Subsites\State\SubsiteState;
 use UnexpectedValueException;
+use PHPUnit\Framework\Attributes\DataProvider;
 
 class SubsiteTest extends BaseSubsiteTest
 {
@@ -317,8 +318,8 @@ public function testDefaultDomain()
      * @param string $identifier Fixture identifier
      * @param bool $currentIsSecure Whether the current base URL should be secure
      * @param string $expected The expected base URL for the subsite or subsite domain
-     * @dataProvider domainProtocolProvider
      */
+    #[DataProvider('domainProtocolProvider')]
     public function testDomainProtocol($class, $identifier, $currentIsSecure, $expected)
     {
         /** @var Subsite|SubsiteDomain $model */
@@ -328,7 +329,7 @@ public function testDomainProtocol($class, $identifier, $currentIsSecure, $expec
         $this->assertSame($this->normaliseTrailingSlash($expected), $model->absoluteBaseURL());
     }
 
-    public function domainProtocolProvider()
+    public static function domainProtocolProvider()
     {
         return [
             [Subsite::class, 'domaintest2', false, 'http://two.mysite.com'],
diff --git a/tests/php/WildcardDomainFieldTest.php b/tests/php/WildcardDomainFieldTest.php
index 2505d6cd..c1679e9d 100644
--- a/tests/php/WildcardDomainFieldTest.php
+++ b/tests/php/WildcardDomainFieldTest.php
@@ -4,6 +4,7 @@
 
 use SilverStripe\Dev\SapphireTest;
 use SilverStripe\Subsites\Forms\WildcardDomainField;
+use PHPUnit\Framework\Attributes\DataProvider;
 
 /**
  * Tests {@see WildcardDomainField}
@@ -14,9 +15,9 @@ class WildcardDomainFieldTest extends SapphireTest
     /**
      * Check that valid domains are accepted
      *
-     * @dataProvider validDomains
      * @param $domain
      */
+    #[DataProvider('validDomains')]
     public function testValidDomains($domain)
     {
         $field = new WildcardDomainField('DomainField');
@@ -26,9 +27,9 @@ public function testValidDomains($domain)
     /**
      * Check that valid domains are accepted
      *
-     * @dataProvider invalidDomains
      * @param $domain
      */
+    #[DataProvider('invalidDomains')]
     public function testInvalidDomains($domain)
     {
         $field = new WildcardDomainField('DomainField');
@@ -38,16 +39,16 @@ public function testInvalidDomains($domain)
     /**
      * Check that valid domains are accepted
      *
-     * @dataProvider validWildcards
      * @param $domain
      */
+    #[DataProvider('validWildcards')]
     public function testValidWildcards($domain)
     {
         $field = new WildcardDomainField('DomainField');
         $this->assertTrue($field->checkHostname($domain), "Validate that {$domain} is a valid domain wildcard");
     }
 
-    public function validDomains()
+    public static function validDomains()
     {
         return [
             ['www.mysite.com'],
@@ -60,7 +61,7 @@ public function validDomains()
         ];
     }
 
-    public function invalidDomains()
+    public static function invalidDomains()
     {
         return [
             ['-mysite'],
@@ -77,7 +78,7 @@ public function invalidDomains()
         ];
     }
 
-    public function validWildcards()
+    public static function validWildcards()
     {
         return [
             ['*.mysite.com'],