The Executor was a Star Dreadnought, lead ship in her class and the flagship of Darth Vader. Executor was laid down and completed at Fondor Drive Yards, possibly under sub-contract from Kuat. Completed less than a month after the Battle of Yavin, it was rammed by three Star Destroyers on its first mission, but suffered only shield depletion. At the Battle of Hoth, the Executor exited hyperspace too close to the planet, alerting the Rebels and allowing them to raise theater shields before a bombardment could be planned. It was destroyed at the Battle of Endor by the concentrated firepower of the entire Rebel fleet and one well-placed collision. The hulk of the Executor, burning and out of control crashed into the incomplete Second Death Star, and was obliterated totally in the station's destruction.
The 8 Kilometer Executor
Many non-movie sources have misrepresented the Executor, leading to a tangled mess of canon and corrections that at last culminated with the ship's length being set at 19 km. This was mainly due to West End Games understating the ship's length and armament by more than 60%. This sad state of affairs led to a lot of Executor-class ships being passed off as underarmed overgrown Star Destroyers when they were in fact quite heavily armed if oddly slim for their great length.