Proton torpedoes were a type of explosive ordnance used throughout the galaxy. Upon impact with a target, the proton warhead would release clouds of high-velocity proton particles in a focused explosion.
Proton torpedoes were capable of incredible maneuverability, such as making a 90-degree turn within a turning circle of one meter. They could also ignore ray shields but were stopped by particle shields. High-yield proton torpedoes, likes those carried on Acclamator-class assault ships, could be used to conduct Base Delta Zero bombardments.
Decades later, proton torpedoes were used by TIE bombers to bomb a carrier stolen by the Spectres. Later, they were used by the Alliance to Restore the Republic during the Battle of Yavin. After examining stolen plans for the Death Star, a planet-destroying space station operated by the Galactic Empire, the Rebel Alliance determined that the Death Star could be destroyed if proton torpedoes were fired into the exhaust port which led down into the reactor core. Red leader Garven Dreis attempted to fire his torpedoes down the shaft, but instead the torpedoes missed the target, impacting on the surface. Using the Force, Luke Skywalker successfully destroyed the station using proton torpedoes from his T-65B X-wing starfighter during the battle.
Around 30 years after the destruction of the DS-2 Death Star II Mobile Battle Station, the Resistance used miniaturized MG7-A proton torpedoes during their bombing run on Starkiller Base's thermal oscillator.