The Type-1 Energy Weapon/Sword, commonly called the energy sword, is a close-quarters weapon used by the Sangheili, a covenant race. It is their signature weapon, and has been a sign of nobility for ages. They pride themselves on their skills, and although those who use the sword cannot marry, they are allowed to breed with any female to pass on the "swordsman" genes.

The energy sword is extremely effective at close ranges. It can kill a Spartan or Sangheili in one hit, due to the sword using ionized gas which boils and penetrates anything it comes into contact with. Because of its lethality, it is highly feared by most human forces. However, it does have several disadvantages, the largest of which being the necessity for combat to be restricted to a small area. It can also give away the position active camouflaged users due to the bright glow.

Similar to many other covenant weapons, the energy sword uses an internal battery which must be recharged when depleted. When out of power, the blades of the sword will retract, leaving only the mostly useless handle. Some versions of the weapon also have a failsafe where if the weapon is dropped, it will automatically consume itself so non-Sangheili forces cannot use it.

The energy sword has been featured in every Halo game (although it could not be wielded in Halo 1), and each game has featured improvements to both design and functionality. In Halo 5, a new legendary variant of the weapon, called the Prophet's Bane, will be usable on the map Truth. It features curved edges and an almost white color, although it works almost identically to standard swords. In Halo lore, it was the custom energy sword of Thel 'Vadam, also known as the Arbiter.