RMS Olympic was the first of the three Olympic-class ocean liners. It sailed from 1911 to 1935 and broke numerous records throughout its career, including the record for largest ship at the time of its construction. It was the only ship in its family to survive long enough to be scrapped.
RMS Titanic was the second of the three Olympic-class ocean liners. It was built in 1912 and went on one voyage, during which it struck an iceberg and sank on April 14-15, 1912. It was the largest ship in the world at the time of its construction and its sinking was one of the largest marine disasters in modern history.
HMHS Britannic was the third and final of the Olympic-class ocean liners. It was the only Olympic-class ocean liner to never be the largest ship in the world. It never served as a passenger ship, instead spending its life as a Royal hospital ship until it was strunk by a mine and sank in 1915.