diff --git a/classes/element.registry.php b/classes/element.registry.php
index 04b8d47de..c33e56524 100644
--- a/classes/element.registry.php
+++ b/classes/element.registry.php
@@ -3,6 +3,9 @@
 declare(strict_types=1);
 
 return [
+    'urn:oasis:names:tc:SAML:2.0:protocol:ext:async-slo' => [
+        'Asynchronous' => '\SimpleSAML\SAML2\XML\aslo\Asynchronous',
+    ],
     'urn:oasis:names:tc:SAML:metadata:algsupport' => [
         'DigestMethod' => '\SimpleSAML\SAML2\XML\alg\DigestMethod',
         'SigningMethod' => '\SimpleSAML\SAML2\XML\alg\SigningMethod',
diff --git a/resources/schemas/saml-async-slo-v1.0.xsd b/resources/schemas/saml-async-slo-v1.0.xsd
new file mode 100644
index 000000000..2a64b8917
--- /dev/null
+++ b/resources/schemas/saml-async-slo-v1.0.xsd
@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<schema xmlns:aslo="urn:oasis:names:tc:SAML:2.0:protocol:ext:async-slo" 
+        xmlns="http://www.w3.org/2001/XMLSchema"  
+        targetNamespace="urn:oasis:names:tc:SAML:2.0:protocol:ext:async-slo"
+        elementFormDefault="qualified">
+    
+    <element name="Asynchronous" type="aslo:AsynchronousType" />
+    <complexType name="AsynchronousType" />
+
+    <attribute name="supportsAsynchronous" type="boolean"/>
+    
+</schema>
diff --git a/src/Constants.php b/src/Constants.php
index 968fd7817..ac884ff07 100644
--- a/src/Constants.php
+++ b/src/Constants.php
@@ -226,6 +226,11 @@ class Constants extends \SimpleSAML\XMLSecurity\Constants
      */
     public const string NS_ALG = 'urn:oasis:names:tc:SAML:metadata:algsupport';
 
+    /**
+     * The namespace for the SAML 2 Asynchronous Single Logout Profile Extension
+     */
+    public const string NS_ASLO = 'urn:oasis:names:tc:SAML:2.0:protocol:ext:async-slo';
+
     /**
      * The namespace for the ECP protocol.
      */
diff --git a/src/XML/aslo/AbstractAsloElement.php b/src/XML/aslo/AbstractAsloElement.php
new file mode 100644
index 000000000..02fdd7938
--- /dev/null
+++ b/src/XML/aslo/AbstractAsloElement.php
@@ -0,0 +1,23 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SimpleSAML\SAML2\XML\aslo;
+
+use SimpleSAML\SAML2\Constants as C;
+use SimpleSAML\XML\AbstractElement;
+
+/**
+ * Abstract class to be implemented by all the classes in this namespace
+ *
+ * @see https://docs.oasis-open.org/security/saml/Post2.0/saml-async-slo/v1.0/saml-async-slo-v1.0.pdf
+ * @package simplesamlphp/saml2
+ */
+abstract class AbstractAsloElement extends AbstractElement
+{
+    public const string NS = C::NS_ASLO;
+
+    public const string NS_PREFIX = 'aslo';
+
+    public const string SCHEMA = 'resources/schemas/saml-async-slo-v1.0.xsd';
+}
diff --git a/src/XML/aslo/Asynchronous.php b/src/XML/aslo/Asynchronous.php
new file mode 100644
index 000000000..50ffca5ea
--- /dev/null
+++ b/src/XML/aslo/Asynchronous.php
@@ -0,0 +1,45 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SimpleSAML\SAML2\XML\aslo;
+
+use Dom;
+use SimpleSAML\SAML2\Assert\Assert;
+use SimpleSAML\XML\SchemaValidatableElementInterface;
+use SimpleSAML\XML\SchemaValidatableElementTrait;
+use SimpleSAML\XMLSchema\Exception\InvalidDOMElementException;
+
+/**
+ * Class representing a aslo:Asynchronous element.
+ *
+ * @package simplesaml/saml2
+ */
+final class Asynchronous extends AbstractAsloElement implements SchemaValidatableElementInterface
+{
+    use SchemaValidatableElementTrait;
+
+
+    /**
+     * Convert XML into a Asynchronous
+     *
+     * @throws \SimpleSAML\XMLSchema\Exception\InvalidDOMElementException
+     *   if the qualified name of the supplied element is wrong
+     */
+    public static function fromXML(Dom\Element $xml): static
+    {
+        Assert::same($xml->localName, 'Asynchronous', InvalidDOMElementException::class);
+        Assert::same($xml->namespaceURI, Asynchronous::NS, InvalidDOMElementException::class);
+
+        return new static();
+    }
+
+
+    /**
+     * Convert this Asynchronous to XML.
+     */
+    public function toXML(?Dom\Element $parent = null): Dom\Element
+    {
+        return $this->instantiateParentElement($parent);
+    }
+}
diff --git a/src/XML/aslo/SupportsAsynchronousTrait.php b/src/XML/aslo/SupportsAsynchronousTrait.php
new file mode 100644
index 000000000..b238525f7
--- /dev/null
+++ b/src/XML/aslo/SupportsAsynchronousTrait.php
@@ -0,0 +1,40 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SimpleSAML\SAML2\XML\aslo;
+
+use SimpleSAML\SAML2\Constants as C;
+use SimpleSAML\XMLSchema\Type\BooleanValue;
+
+/**
+ * @package simplesamlphp/saml2
+ */
+trait SupportsAsynchronousTrait
+{
+    /** @var \SimpleSAML\XMLSchema\Type\BooleanValue|null */
+    protected ?BooleanValue $supportsAsynchronous = null;
+
+
+    /**
+     * @return \SimpleSAML\XMLSchema\Type\BooleanValue|null
+     */
+    public function getSupportsAsynchronous(): ?BooleanValue
+    {
+        return $this->supportsAsynchronous;
+    }
+
+
+    /**
+     * @param array<\SimpleSAML\XML\Attribute> $namespacedAttributes
+     */
+    private function setSupportsAsynchronous(array $namespacedAttributes = []): void
+    {
+        foreach ($namespacedAttributes as $attr) {
+            if ($attr->getNamespaceURI() === C::NS_ASLO && $attr->getAttrName() === 'supportsAsynchronous') {
+                $this->supportsAsynchronous = BooleanValue::fromString($attr->getAttrValue()->getValue());
+                return;
+            }
+        }
+    }
+}
diff --git a/src/XML/md/SingleLogoutService.php b/src/XML/md/SingleLogoutService.php
index 6cfcf1842..eb4e0cd4f 100644
--- a/src/XML/md/SingleLogoutService.php
+++ b/src/XML/md/SingleLogoutService.php
@@ -4,11 +4,42 @@
 
 namespace SimpleSAML\SAML2\XML\md;
 
+use SimpleSAML\SAML2\Type\SAMLAnyURIValue;
+use SimpleSAML\SAML2\XML\aslo\SupportsAsynchronousTrait;
+use SimpleSAML\XML\SchemaValidatableElementInterface;
+use SimpleSAML\XML\SchemaValidatableElementTrait;
+
 /**
  * SingleLogoutService element of type EndpointType
  *
  * @package simplesamlphp/saml2
  */
-final class SingleLogoutService extends AbstractEndpointType
+final class SingleLogoutService extends AbstractEndpointType implements SchemaValidatableElementInterface
 {
+    use SchemaValidatableElementTrait;
+    use SupportsAsynchronousTrait;
+
+
+    /**
+     * SingleLogoutService constructor.
+     *
+     * @param \SimpleSAML\SAML2\Type\SAMLAnyURIValue $binding
+     * @param \SimpleSAML\SAML2\Type\SAMLAnyURIValue $location
+     * @param \SimpleSAML\SAML2\Type\SAMLAnyURIValue|null $responseLocation
+     * @param \SimpleSAML\XML\ElementInterface[] $children
+     * @param array<\SimpleSAML\XML\Attribute> $attributes
+     *
+     * @throws \SimpleSAML\Assert\AssertionFailedException
+     */
+    public function __construct(
+        protected SAMLAnyURIValue $binding,
+        protected SAMLAnyURIValue $location,
+        protected ?SAMLAnyURIValue $responseLocation = null,
+        array $children = [],
+        array $attributes = [],
+    ) {
+        $this->setSupportsAsynchronous($attributes);
+
+        parent::__construct($binding, $location, $responseLocation, $children, $attributes);
+    }
 }
diff --git a/src/XML/samlp/Extensions.php b/src/XML/samlp/Extensions.php
index 5f7884e5d..d6534d1d7 100644
--- a/src/XML/samlp/Extensions.php
+++ b/src/XML/samlp/Extensions.php
@@ -9,6 +9,7 @@
 use SimpleSAML\SAML2\Utils\XPath;
 use SimpleSAML\SAML2\XML\ExtensionsTrait;
 use SimpleSAML\XML\Chunk;
+use SimpleSAML\XML\Registry\ElementRegistry;
 use SimpleSAML\XML\SchemaValidatableElementInterface;
 use SimpleSAML\XML\SchemaValidatableElementTrait;
 use SimpleSAML\XMLSchema\Exception\InvalidDOMElementException;
@@ -63,11 +64,18 @@ public static function fromXML(Dom\Element $xml): static
             'Invalid Extensions element \'' . $xml->localName . '\'',
             InvalidDOMElementException::class,
         );
+
+        $registry = ElementRegistry::getInstance();
         $ret = [];
 
         /** @var \Dom\Element $node */
         foreach (XPath::xpQuery($xml, './*', XPath::getXPath($xml)) as $node) {
-            $ret[] = new Chunk($node);
+            $result = $registry->getElementHandler($node->namespaceURI, $node->localName);
+            if ($result !== null) {
+                $ret[] = $result::fromXML($node);
+            } else {
+                $ret[] = new Chunk($node);
+            }
         }
 
         return new static($ret);
diff --git a/tests/SAML2/XML/aslo/AsynchronousTest.php b/tests/SAML2/XML/aslo/AsynchronousTest.php
new file mode 100644
index 000000000..09e7609b8
--- /dev/null
+++ b/tests/SAML2/XML/aslo/AsynchronousTest.php
@@ -0,0 +1,57 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SimpleSAML\SAML2\Test\SAML2\XML\aslo;
+
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\Group;
+use PHPUnit\Framework\TestCase;
+use SimpleSAML\SAML2\XML\aslo\AbstractAsloElement;
+use SimpleSAML\SAML2\XML\aslo\Asynchronous;
+use SimpleSAML\XML\DOMDocumentFactory;
+use SimpleSAML\XML\TestUtils\SchemaValidationTestTrait;
+use SimpleSAML\XML\TestUtils\SerializableElementTestTrait;
+
+use function dirname;
+use function strval;
+
+/**
+ * Class \SimpleSAML\SAML2\XML\aslo\AsynchronousTest
+ *
+ * @package simplesamlphp/saml2
+ */
+#[Group('aslo')]
+#[CoversClass(Asynchronous::class)]
+#[CoversClass(AbstractAsloElement::class)]
+final class AsynchronousTest extends TestCase
+{
+    use SchemaValidationTestTrait;
+    use SerializableElementTestTrait;
+
+
+    /**
+     */
+    public static function setUpBeforeClass(): void
+    {
+        self::$testedClass = Asynchronous::class;
+
+        self::$xmlRepresentation = DOMDocumentFactory::fromFile(
+            dirname(__FILE__, 4) . '/resources/xml/aslo_Asynchronous.xml',
+        );
+    }
+
+
+    /**
+     */
+    public function testMarshalling(): void
+    {
+        $asynchronous = new Asynchronous();
+
+        $expectedXml = self::$xmlRepresentation->saveXml(self::$xmlRepresentation->documentElement);
+        $this->assertNotFalse($expectedXml);
+        $actualXml = strval($asynchronous);
+
+        $this->assertXmlStringEqualsXmlString($expectedXml, $actualXml);
+    }
+}
diff --git a/tests/SAML2/XML/md/SingleLogoutServiceTest.php b/tests/SAML2/XML/md/SingleLogoutServiceTest.php
new file mode 100644
index 000000000..95245d0da
--- /dev/null
+++ b/tests/SAML2/XML/md/SingleLogoutServiceTest.php
@@ -0,0 +1,78 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SimpleSAML\Test\SAML2\XML\md;
+
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\Group;
+use PHPUnit\Framework\TestCase;
+use SimpleSAML\SAML2\Type\SAMLAnyURIValue;
+use SimpleSAML\SAML2\XML\md\AbstractMdElement;
+use SimpleSAML\SAML2\XML\md\SingleLogoutService;
+use SimpleSAML\Test\SAML2\Constants as C;
+use SimpleSAML\XML\Attribute as XMLAttribute;
+use SimpleSAML\XML\DOMDocumentFactory;
+use SimpleSAML\XML\TestUtils\SchemaValidationTestTrait;
+use SimpleSAML\XML\TestUtils\SerializableElementTestTrait;
+use SimpleSAML\XMLSchema\Type\BooleanValue;
+
+use function dirname;
+use function strval;
+
+/**
+ * Tests for md:SingleLogoutService.
+ *
+ * @package simplesamlphp/saml2
+ */
+#[Group('md')]
+#[CoversClass(SingleLogoutService::class)]
+#[CoversClass(AbstractMdElement::class)]
+final class SingleLogoutServiceTest extends TestCase
+{
+    use SchemaValidationTestTrait;
+    use SerializableElementTestTrait;
+
+
+    /**
+     */
+    public static function setUpBeforeClass(): void
+    {
+        self::$testedClass = SingleLogoutService::class;
+
+        self::$xmlRepresentation = DOMDocumentFactory::fromFile(
+            dirname(__FILE__, 4) . '/resources/xml/md_SingleLogoutService.xml',
+        );
+    }
+
+
+    // test marshalling
+
+
+    /**
+     * Test creating a SingleLogoutService from scratch.
+     */
+    public function testMarshalling(): void
+    {
+        $supportsAsynchronous = new XMLAttribute(
+            C::NS_ASLO,
+            'aslo',
+            'supportsAsynchronous',
+            BooleanValue::fromBoolean(true),
+        );
+
+        $sloep = new SingleLogoutService(
+            SAMLAnyURIValue::fromString(C::BINDING_HTTP_POST),
+            SAMLAnyURIValue::fromString(C::LOCATION_A),
+            SAMLAnyURIValue::fromString(C::LOCATION_B),
+            [],
+            [$supportsAsynchronous],
+        );
+
+        $expectedXml = self::$xmlRepresentation->saveXml(self::$xmlRepresentation->documentElement);
+        $this->assertNotFalse($expectedXml);
+        $actualXml = strval($sloep);
+
+        $this->assertXmlStringEqualsXmlString($expectedXml, $actualXml);
+    }
+}
diff --git a/tests/SAML2/XML/samlp/AuthnRequestTest.php b/tests/SAML2/XML/samlp/AuthnRequestTest.php
index 08fcb58c4..4a4b679be 100644
--- a/tests/SAML2/XML/samlp/AuthnRequestTest.php
+++ b/tests/SAML2/XML/samlp/AuthnRequestTest.php
@@ -17,6 +17,7 @@
 use SimpleSAML\SAML2\Type\SAMLStringValue;
 use SimpleSAML\SAML2\Utils;
 use SimpleSAML\SAML2\Utils\XPath;
+use SimpleSAML\SAML2\XML\aslo\Asynchronous;
 use SimpleSAML\SAML2\XML\saml\Audience;
 use SimpleSAML\SAML2\XML\saml\AudienceRestriction;
 use SimpleSAML\SAML2\XML\saml\AuthnContextClassRef;
@@ -31,6 +32,7 @@
 use SimpleSAML\SAML2\XML\samlp\AbstractSamlpElement;
 use SimpleSAML\SAML2\XML\samlp\AuthnContextComparisonTypeEnum;
 use SimpleSAML\SAML2\XML\samlp\AuthnRequest;
+use SimpleSAML\SAML2\XML\samlp\Extensions;
 use SimpleSAML\SAML2\XML\samlp\GetComplete;
 use SimpleSAML\SAML2\XML\samlp\IDPEntry;
 use SimpleSAML\SAML2\XML\samlp\IDPList;
@@ -101,6 +103,10 @@ public function testMarshalling(): void
             ),
         );
 
+        $extensions = new Extensions([
+            new Asynchronous(),
+        ]);
+
         $authnRequest = new AuthnRequest(
             subject: $subject,
             issuer: new Issuer(
@@ -110,6 +116,7 @@ public function testMarshalling(): void
             id: IDValue::fromString('_2b0226190ca1c22de6f66e85f5c95158'),
             issueInstant: SAMLDateTimeValue::fromString('2014-09-22T13:42:00Z'),
             destination: SAMLAnyURIValue::fromString('https://tiqr.stepup.org/idp/profile/saml2/Redirect/SSO'),
+            extensions: $extensions,
         );
 
         $expectedXml = self::$xmlRepresentation->saveXml(self::$xmlRepresentation->documentElement);
@@ -181,6 +188,11 @@ public function testMarshallingElementOrdering(): void
             [$requesterId],
         );
 
+        // Create Extensions
+        $extensions = new Extensions([
+            new Asynchronous(),
+        ]);
+
         $authnRequest = new AuthnRequest(
             id: IDValue::fromString('SomeIDValue'),
             requestedAuthnContext: $rac,
@@ -192,27 +204,30 @@ public function testMarshallingElementOrdering(): void
                 SAMLStringValue::fromString('https://gateway.stepup.org/saml20/sp/metadata'),
             ),
             scoping: $scoping,
+            extensions: $extensions,
         );
 
         $authnRequestElement = $authnRequest->toXML();
 
         // Test for a Subject
         $xpCache = XPath::getXPath($authnRequestElement);
-        $authnRequestElements = XPath::xpQuery($authnRequestElement, './saml_assertion:Subject', $xpCache);
+        $authnRequestElements = XPath::xpQuery($authnRequestElement, './saml_assertion:Issuer', $xpCache);
         $this->assertCount(1, $authnRequestElements);
 
         // Test ordering of AuthnRequest contents
         /** @var \Dom\Element[] $authnRequestElements */
         $authnRequestElements = XPath::xpQuery(
             $authnRequestElement,
-            './saml_assertion:Subject/following-sibling::*',
+            './saml_assertion:Issuer/following-sibling::*',
             $xpCache,
         );
-        $this->assertCount(4, $authnRequestElements);
-        $this->assertEquals('samlp:NameIDPolicy', $authnRequestElements[0]->tagName);
-        $this->assertEquals('saml:Conditions', $authnRequestElements[1]->tagName);
-        $this->assertEquals('samlp:RequestedAuthnContext', $authnRequestElements[2]->tagName);
-        $this->assertEquals('samlp:Scoping', $authnRequestElements[3]->tagName);
+        $this->assertCount(6, $authnRequestElements);
+        $this->assertEquals('samlp:Extensions', $authnRequestElements[0]->tagName);
+        $this->assertEquals('saml:Subject', $authnRequestElements[1]->tagName);
+        $this->assertEquals('samlp:NameIDPolicy', $authnRequestElements[2]->tagName);
+        $this->assertEquals('saml:Conditions', $authnRequestElements[3]->tagName);
+        $this->assertEquals('samlp:RequestedAuthnContext', $authnRequestElements[4]->tagName);
+        $this->assertEquals('samlp:Scoping', $authnRequestElements[5]->tagName);
     }
 
 
diff --git a/tests/resources/xml/aslo_Asynchronous.xml b/tests/resources/xml/aslo_Asynchronous.xml
new file mode 100644
index 000000000..d4dcb6243
--- /dev/null
+++ b/tests/resources/xml/aslo_Asynchronous.xml
@@ -0,0 +1 @@
+<aslo:Asynchronous xmlns:aslo="urn:oasis:names:tc:SAML:2.0:protocol:ext:async-slo" />
diff --git a/tests/resources/xml/md_SingleLogoutService.xml b/tests/resources/xml/md_SingleLogoutService.xml
new file mode 100644
index 000000000..871e8766d
--- /dev/null
+++ b/tests/resources/xml/md_SingleLogoutService.xml
@@ -0,0 +1 @@
+<md:SingleLogoutService xmlns:md="urn:oasis:names:tc:SAML:2.0:metadata" xmlns:aslo="urn:oasis:names:tc:SAML:2.0:protocol:ext:async-slo" Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST" Location="https://simplesamlphp.org/some/endpoint" ResponseLocation="https://simplesamlphp.org/other/endpoint" aslo:supportsAsynchronous="true"/>
diff --git a/tests/resources/xml/samlp_AuthnRequest.xml b/tests/resources/xml/samlp_AuthnRequest.xml
index 5eea6f099..6d8970f4c 100644
--- a/tests/resources/xml/samlp_AuthnRequest.xml
+++ b/tests/resources/xml/samlp_AuthnRequest.xml
@@ -1,5 +1,8 @@
-<samlp:AuthnRequest xmlns:samlp="urn:oasis:names:tc:SAML:2.0:protocol" xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion" Version="2.0" ID="_2b0226190ca1c22de6f66e85f5c95158" IssueInstant="2014-09-22T13:42:00Z" Destination="https://tiqr.stepup.org/idp/profile/saml2/Redirect/SSO" Consent="urn:oasis:names:tc:SAML:2.0:consent:unspecified">
+<samlp:AuthnRequest xmlns:samlp="urn:oasis:names:tc:SAML:2.0:protocol" xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion" xmlns:aslo="urn:oasis:names:tc:SAML:2.0:protocol:ext:async-slo" Version="2.0" ID="_2b0226190ca1c22de6f66e85f5c95158" IssueInstant="2014-09-22T13:42:00Z" Destination="https://tiqr.stepup.org/idp/profile/saml2/Redirect/SSO" Consent="urn:oasis:names:tc:SAML:2.0:consent:unspecified">
   <saml:Issuer>https://gateway.stepup.org/saml20/sp/metadata</saml:Issuer>
+  <samlp:Extensions>
+    <aslo:Asynchronous/>
+  </samlp:Extensions>
   <saml:Subject>
     <saml:NameID Format="urn:oasis:names:tc:SAML:1.1:nameid-format:unspecified">user@example.org</saml:NameID>
   </saml:Subject>