Which expansion introduced the Demon Hunter class?

Which expansion introduced the Demon Hunter class? The answer is Legion. Released in 2016, World of Warcraft: Legion added Demon Hunters as a new hero class built around the lore of Illidan Stormrage and his elite Illidari.

Demon Hunters sacrifice part of their humanity to wield demonic powers against the Burning Legion. Their defining abilities include spectral sight, exceptional mobility, double-jumping, gliding, and Metamorphosis. Unlike most classes, they began with a dedicated story sequence set in Mardum, a demon world where Illidan had sent his followers to obtain the Sargerite Keystone.

At launch, Demon Hunters were restricted to two elven races: Night Elves for the Alliance and Blood Elves for the Horde. The class offered two specializations: Havoc, focused on melee damage, and Vengeance, focused on tanking. Demon Hunters also began at a much higher level than ordinary characters, another feature shared with the earlier Death Knight hero class.

The main mix-up is with the Burning Crusade, where Illidan and many demon-hunter characters already appeared. However, Legion was the expansion that made Demon Hunter a playable player class.