HMHS Britannic was the third and final vessel of the White Star Line's Olympic class of ocean liners and the second White Star ship to bear the name Britannic. She was the younger sister of RMS Olympic and RMS Titanic and was intended to enter service as a transatlantic passenger liner. She operated as a hospital ship from 1915 until her sinking near the Greek island of Kea, in the Aegean Sea at position, in November 1916. At the time she was the largest hospital ship in the world, and the largest vessel built in Britain.