What were Titanic's four code letters?

Titanic's four code letters were HVMP. These were the ship's visual signal or code letters, used to identify her through maritime flags and formal ship communications.

They were separate from Titanic's wireless call sign, MGY. Radio operators Jack Phillips and Harold Bride used MGY when transmitting Morse messages from the Marconi room, including the distress traffic sent during the sinking. The distinction matters because both systems identified the same vessel but served different communication purposes.

Titanic's code letters belonged to the pre-1934 system in which ships could have separate signal letters and wireless call signs. Signal letters were especially useful for visual recognition at sea, while the wireless call sign was transmitted by radio. The letters were not an abbreviation for the ship's name and were not chosen to describe her.

A frequent trivia trap is answering MGY, the famous radio identifier, instead of HVMP. MGY is historically associated with Titanic's distress calls, but HVMP is the correct answer to a question asking for her four code letters.