An antimatter torpedo was a type of torpedo armed with an antimatter explosive.
Antimatter torpedoes were used by the Kovaalans in 2154. The yield of the torpedo could be varied, much like that of a photon torpedo. (ENT: "E²")
The inhabitants of Kelemane's planet developed antimatter torpedoes to be used against the USS Voyager, which they knew as the Sky Ship. (VOY: "Blink of an Eye")
The series 5 long-range tactical armor unit was a type of highly-advanced antimatter torpedo designed by the Druoda, a Delta Quadrant species. (VOY: "Warhead")