The 11th century is defined by the calendar of Earth as occurring from the year 1001 through the year 1100.
- All life on the planet Zetar is extinguished in a war. Only about a hundred individuals survive as energy patterns representing their thoughts. (TOS: "The Lights of Zetar")
- On Earth, Irish warriors led by King Brian Boru defeat invading Vikings at the Battle of Clontarf. Brian Boru is killed by the Vikings during the battle. (DS9: "Bar Association")
- First Crusade captures Jerusalem. (TOS: "The Squire of Gothos"; DS9: "Q-Less"; VOY: "The Killing Game")
|10th century||Timeline||12th century|