diff --git a/Tests/LibWeb/Text/expected/Crypto/SubtleCrypto-sign.txt b/Tests/LibWeb/Text/expected/Crypto/SubtleCrypto-sign.txt
index dd749e8d8ea..984528d61d5 100644
--- a/Tests/LibWeb/Text/expected/Crypto/SubtleCrypto-sign.txt
+++ b/Tests/LibWeb/Text/expected/Crypto/SubtleCrypto-sign.txt
@@ -1 +1 @@
-Signed OK ... [13 bytes total] (Hello friends)
+Signed OK
diff --git a/Tests/LibWeb/Text/input/Crypto/SubtleCrypto-sign.html b/Tests/LibWeb/Text/input/Crypto/SubtleCrypto-sign.html
index 94ed5b3adba..83442d84a0e 100644
--- a/Tests/LibWeb/Text/input/Crypto/SubtleCrypto-sign.html
+++ b/Tests/LibWeb/Text/input/Crypto/SubtleCrypto-sign.html
@@ -3,29 +3,25 @@
     asyncTest(async done => {
         const encoder = new TextEncoder();
         const message = "Hello friends";
-        const encoded_message = encoder.encode(message);
+        const encodedMessage = encoder.encode(message);
 
-        const key_algorithm = {
-            name: "ECDSA",
-            namedCurve: "P-384",
+        const keyAlgorithm = {
+            name: "Ed25519",
         };
         const extractable = true;
         const usages = ["sign", "verify"];
-        const key = await window.crypto.subtle.generateKey(key_algorithm, extractable, usages);
+        const key = await window.crypto.subtle.generateKey(keyAlgorithm, extractable, usages);
 
-        const signature_algorithm = {
-            name: "ECDSA",
-            hash: { name: "SHA-384" },
+        const signatureAlgorithm = {
+            name: "Ed25519",
         };
         const signature = await window.crypto.subtle.sign(
-            signature_algorithm,
+            signatureAlgorithm,
             key.privateKey,
-            encoded_message
+            encodedMessage
         );
 
-        const data_view = String.fromCharCode.apply(null, new Uint8Array(signature));
-
-        println(`Signed OK ... [${signature.byteLength} bytes total] (${data_view})`);
+        println(`Signed OK`);
 
         done();
     });
diff --git a/Userland/Libraries/LibWeb/Crypto/CryptoAlgorithms.cpp b/Userland/Libraries/LibWeb/Crypto/CryptoAlgorithms.cpp
index 3f2cd6298b8..2e96c5d1a79 100644
--- a/Userland/Libraries/LibWeb/Crypto/CryptoAlgorithms.cpp
+++ b/Userland/Libraries/LibWeb/Crypto/CryptoAlgorithms.cpp
@@ -1278,4 +1278,38 @@ WebIDL::ExceptionOr<Variant<JS::NonnullGCPtr<CryptoKey>, JS::NonnullGCPtr<Crypto
     return Variant<JS::NonnullGCPtr<CryptoKey>, JS::NonnullGCPtr<CryptoKeyPair>> { CryptoKeyPair::create(m_realm, public_key, private_key) };
 }
 
+WebIDL::ExceptionOr<JS::NonnullGCPtr<JS::ArrayBuffer>> ED25519::sign([[maybe_unused]] AlgorithmParams const& params, JS::NonnullGCPtr<CryptoKey> key, ByteBuffer const& message)
+{
+    auto& realm = m_realm;
+    auto& vm = realm.vm();
+
+    // 1. If the [[type]] internal slot of key is not "private", then throw an InvalidAccessError.
+    if (key->type() != Bindings::KeyType::Private)
+        return WebIDL::InvalidAccessError::create(realm, "Key is not a private key"_fly_string);
+
+    // 2. Perform the Ed25519 signing process, as specified in [RFC8032], Section 5.1.6,
+    // with message as M, using the Ed25519 private key associated with key.
+    auto private_key = key->handle().visit(
+        [](ByteBuffer data) -> ByteBuffer {
+            return data;
+        },
+        [](auto) -> ByteBuffer { VERIFY_NOT_REACHED(); });
+
+    ::Crypto::Curves::Ed25519 curve;
+    auto maybe_public_key = curve.generate_public_key(private_key);
+    if (maybe_public_key.is_error())
+        return WebIDL::OperationError::create(realm, "Failed to generate public key"_fly_string);
+    auto public_key = maybe_public_key.release_value();
+
+    auto maybe_signature = curve.sign(public_key, private_key, message);
+    if (maybe_signature.is_error())
+        return WebIDL::OperationError::create(realm, "Failed to sign message"_fly_string);
+    auto signature = maybe_signature.release_value();
+
+    // 3. Return a new ArrayBuffer associated with the relevant global object of this [HTML],
+    // and containing the bytes of the signature resulting from performing the Ed25519 signing process.
+    auto result = TRY_OR_THROW_OOM(vm, ByteBuffer::copy(signature));
+    return JS::ArrayBuffer::create(realm, move(result));
+}
+
 }
diff --git a/Userland/Libraries/LibWeb/Crypto/CryptoAlgorithms.h b/Userland/Libraries/LibWeb/Crypto/CryptoAlgorithms.h
index 3955c83da70..5f920288339 100644
--- a/Userland/Libraries/LibWeb/Crypto/CryptoAlgorithms.h
+++ b/Userland/Libraries/LibWeb/Crypto/CryptoAlgorithms.h
@@ -266,6 +266,7 @@ private:
 
 class ED25519 : public AlgorithmMethods {
 public:
+    virtual WebIDL::ExceptionOr<JS::NonnullGCPtr<JS::ArrayBuffer>> sign(AlgorithmParams const&, JS::NonnullGCPtr<CryptoKey>, ByteBuffer const&) override;
     virtual WebIDL::ExceptionOr<Variant<JS::NonnullGCPtr<CryptoKey>, JS::NonnullGCPtr<CryptoKeyPair>>> generate_key(AlgorithmParams const&, bool, Vector<Bindings::KeyUsage> const&) override;
 
     static NonnullOwnPtr<AlgorithmMethods> create(JS::Realm& realm) { return adopt_own(*new ED25519(realm)); }
diff --git a/Userland/Libraries/LibWeb/Crypto/SubtleCrypto.cpp b/Userland/Libraries/LibWeb/Crypto/SubtleCrypto.cpp
index bf9f2f230c9..e19b16c7792 100644
--- a/Userland/Libraries/LibWeb/Crypto/SubtleCrypto.cpp
+++ b/Userland/Libraries/LibWeb/Crypto/SubtleCrypto.cpp
@@ -645,6 +645,7 @@ SupportedAlgorithmsMap supported_algorithms()
     define_an_algorithm<ECDSA, EcKeyGenParams>("generateKey"_string, "ECDSA"_string);
 
     // https://wicg.github.io/webcrypto-secure-curves/#ed25519
+    define_an_algorithm<ED25519>("sign"_string, "Ed25519"_string);
     define_an_algorithm<ED25519>("generateKey"_string, "Ed25519"_string);
 
     return internal_object;