What was the hull number of the Titanic?

The Titanic’s Harland and Wolff hull number was 401.

Hull numbers were construction identifiers assigned by the Belfast shipyard Harland and Wolff. Titanic was the second Olympic-class liner built for the White Star Line, following Olympic, which received hull number 400. Titanic therefore became yard number 401.

The number was assigned during construction and is not the same as a radio call sign, registry number, or modern IMO ship identification number. Titanic’s keel was laid in March 1909, she was launched in May 1911, and she entered service on her maiden voyage from Southampton on 10 April 1912.

The next Olympic-class ship, Britannic, received hull number 433. The gap between Titanic and Britannic reflects the shipyard’s continuing work on other vessels and projects. The number 401 is consequently a construction-history fact, not a designation passengers would normally have seen used aboard ship.