The impulse deck was an area on Constitution-class starships which housed the impulse engines.

In 2265, after the starship USS Enterprise was severely damaged due to an encounter with the galactic barrier, Gary Mitchell, who had gained incredible psychic powers due to his exposure to the barrier, informed Lieutenant Lee Kelso that, if he activated the impulse packs in the damaged state they were in, they would blow out the entire impulse deck. (TOS: "Where No Man Has Gone Before")