Antimatter

Antimatter is matter which is composed of the antiparticles of "ordinary" matter. A collision between any particle and its anti-particle partner leads to their mutual annihilation, which can release vast amounts of energy.

Isolated and stored anti-matter could be used as a fuel for interplanetary or interstellar travel as part of an antimatter catalyzed nuclear pulse propulsion or other antimatter rocketry.

It is also the power source for antimatter weapons.