Britannic, in full His Majesty’s Hospital Ship (HMHS) Britannic, British liner that was a sister ship of the Olympic and the Titanic. Never operating as a commercial vessel, it was refitted as a hospital ship during World War I and sank in 1916 after reportedly striking a mine.

postcard of the Britannic Postcard of the Britannic. The Granger Collection, New York

The Britannic was built by the Belfast firm of Harland and Wolff as part of a class of transatlantic luxury liners for the White Star Line. The class, which was designed for comfort rather than speed, was conceived in 1907 and initially included only the Olympic and Titanic. The third ship was added later, and it was planned to be larger and more luxurious than its sister ships. On November 30, 1911, construction began with the laying of the keel. After the Titanic sank in April 1912, however, the ship was redesigned to incorporate various safety modifications. Notably, more lifeboats were added, and its watertight compartments (which featured doors that allowed the sections to be isolated from each other) were increased to 17 in number, 5 of which were raised from E deck to B deck. In addition, its name was reportedly changed from Gigantic to Britannic. After the hull was completed, the ship was launched on February 26, 1914. The Britannic was scheduled to begin its commercial service the following year. However, with the start of World War I in 1914, the Britannic was requisitioned as a hospital ship in 1915. Upon its completion, the ship measured approximately 882 feet (269 metres) in length and had a gross tonnage of 48,158.

On December 23, 1915, the Britannic undertook its maiden voyage, sailing from Liverpool, England, to the Greek island of Lemnos, via Naples. After collecting some 3,300 casualties, the ship departed for Southampton, England, and arrived there on January 9, 1916. The Britannic sailed on two subsequent voyages before being released from war duty in June 1916. However, two months later it was again requisitioned. On November 12, 1916, the Britannic departed from Southampton for Lemnos on its sixth voyage. At approximately 8:15 am on November 21, some 2 miles (3 km) from Kéa island, Greece, an explosion occurred on the ship. Initial reports suggested the cause as either a mine or a torpedo, though later evidence pointed to a mine. (In October a German U-boat had laid mines in the area.) Although damage was extensive, only six of the watertight compartments flooded, and the ship remained afloat. As the ship listed, water began to enter open portholes on the starboard side. In an attempt to beach the ship off Kéa, Capt. Charles Bartlett ordered full speed. The movement, however, caused more water to enter the ship, and Bartlett quickly ordered the engines stopped. At approximately 9:07 am the Britannic sank. (While the Titanic took 2 hours and 40 minutes to founder, the Britannic was lost in about 55 minutes.) Several boats came to rescue the survivors, including the Scourge and Heroic. Despite the speed of its sinking, only 30 people were killed. More than 1,030 were saved.

In 1975 French ocean explorer Jacques Cousteau discovered the wreckage of the Britannic. The ship was found lying on its starboard side at a depth of some 390 feet (119 metres). It was intact except for a large hole in its bow.