- For other uses, see Proton.
The antiproton was a particle, an antimatter element with the opposite charge of a proton. In the early 25th century, antiproton energy constituted a common directed energy weapons type by the Alpha Quadrant Alliance. (TOS episode: "The Doomsday Machine", STO - Klingon War mission: "The Doomsday Device")
Residual antiprotons emanating from cloaked ships could be used to detect such vessels. In 2379, the prototype IRW Scimitar employed an advanced form of cloaking device that left no detectable antiproton trace. (TNG movie: Star Trek: Nemesis)
In 2366, the illusory Delta Rana warship, created by the Douwd Kevin Uxbridge to mimic the Husnock warship that ravaged Delta Rana IV, used beams of antiprotons and positrons. Its firepower could be modulated from the equivalent to forty megawatts to 400 gigawatts. (TNG episode: "The Survivors")
By 2409, antiproton-based directed energy weapons were available for handheld and shipboard use. Antiprotons, when confined into a beam, normally appeared crimson with a black void border. Up close, the energy looked a lot more unstable, similar to plasma and tetryon energy. However, Undine antiproton weapons were pale yellow in color. (STO - Klingon War missions: "Welcome to Earth Spacedock", "Diplomatic Orders")
When the Annorax-class science dreadnought was launched during the Iconian War of 2410, vessels of the class were pre-equipped with a chroniton lance that fired antiproton beams. (STO - The Iconian War mission: "Time and Tide")
Other factions using antiproton-based directed energy weapons as a default during the 2400s and 2410s decades included: the Crystalline Entity, Fek'Ihri Horde, Iconian Empire, Malon Cooperative, Sphere Builders, Undine, and Voth. (STO video games: Legacy of Romulus, Delta Rising, Agents of Yesterday)
In the 29th and 31st centuries, ships of the resurgent Terran Empire, like the Paradox-class temporal dreadnought, fired antiproton weapons. (STO - Agents of Yesterday mission: "Assault on Terok Nor")