diff --git a/multiaddr/codecs/memory.py b/multiaddr/codecs/memory.py
new file mode 100644
index 0000000..e3055e0
--- /dev/null
+++ b/multiaddr/codecs/memory.py
@@ -0,0 +1,28 @@
+import struct
+from ..codecs import CodecBase
+from ..exceptions import BinaryParseError
+
+SIZE = 64
+IS_PATH = False
+
+class Codec(CodecBase):
+    SIZE = SIZE
+    IS_PATH = IS_PATH
+    
+    def to_bytes(self, proto, string: str) -> bytes:
+            # Parse as unsigned 64-bit int
+            value = int(string, 10)
+            if value < 0 or value > 0xFFFFFFFFFFFFFFFF:
+                raise ValueError("Value out of range for uint64")
+            return struct.pack(">Q", value) # big-endian uint64
+
+    def to_string(self, proto, buf: bytes) -> str:
+        if len(buf) != 8:
+            raise BinaryParseError("Expected 8 bytes for uint64", buf, "memory")
+        value = struct.unpack(">Q", buf)[0]
+        return str(value)
+    
+    def memory_validate(self, b: bytes) -> None:
+        if len(b) != 8:
+            raise ValueError(f"Invalid length: must be exactly 8 bytes, got {len(b)}")
+         
\ No newline at end of file
diff --git a/multiaddr/protocols.py b/multiaddr/protocols.py
index eb25f63..5de8990 100644
--- a/multiaddr/protocols.py
+++ b/multiaddr/protocols.py
@@ -78,6 +78,7 @@
 P_SNI = 0x01C1
 P_NOISE = 0x01C6
 P_WEBTRANSPORT = 0x01D1
+P_MEMORY = 0x309
 
 
 class Protocol:
@@ -166,6 +167,7 @@ def __repr__(self) -> str:
     Protocol(P_P2P_CIRCUIT, "p2p-circuit", None),
     Protocol(P_WEBTRANSPORT, "webtransport", None),
     Protocol(P_UNIX, "unix", "fspath"),
+    Protocol(P_MEMORY, "memory", None)
 ]
 
 
diff --git a/tests/test_codec.py b/tests/test_codec.py
new file mode 100644
index 0000000..ffe2c04
--- /dev/null
+++ b/tests/test_codec.py
@@ -0,0 +1,66 @@
+import pytest
+import struct
+
+from multiaddr.codecs import memory
+from multiaddr.exceptions import BinaryParseError
+
+
+def test_to_bytes_and_to_string_roundtrip():
+    codec = memory.Codec()
+
+    # some valid values
+    for val in [0, 1, 42, 2**32, 2**64 - 1]:
+        s = str(val)
+        b = codec.to_bytes(None, s)
+        # must be exactly 8 bytes
+        assert isinstance(b, bytes)
+        assert len(b) == 8
+        # roundtrip back to string
+        out = codec.to_string(None, b)
+        assert out == s
+
+def test_invalid_string_to_bytes():
+    codec = memory.Codec()
+
+    # not a number
+    with pytest.raises(ValueError):
+        codec.to_bytes(None, "abc")
+
+    # negative number
+    with pytest.raises(ValueError):
+        codec.to_bytes(None, "-1")
+
+    # too large
+    with pytest.raises(ValueError):
+        codec.to_bytes(None, str(2**64))
+
+def test_invalid_bytes_to_string():
+    codec = memory.Codec()
+
+    # too short
+    with pytest.raises(BinaryParseError):
+        codec.to_string(None, b"\x00\x01")
+
+    # too long
+    with pytest.raises(BinaryParseError):
+        codec.to_string(None, b"\x00" * 9)
+
+
+def test_specific_encoding():
+    codec = memory.Codec()
+
+    # 42 encoded in big-endian
+    expected_bytes = b"\x00\x00\x00\x00\x00\x00\x00*"
+    assert codec.to_bytes(None, "42") == expected_bytes
+    assert codec.to_string(None, expected_bytes) == "42"
+
+def test_memory_validate_function():
+    # Directly test the helper
+    codec = memory.Codec()
+
+    # Valid case
+    codec.memory_validate(b"\x00" * 8)  # should not raise
+
+    # Invalid length
+    with pytest.raises(ValueError):
+        codec.memory_validate(b"\x00" * 7)
\ No newline at end of file