Which Hogwarts headmaster founded the Order of the Phoenix in Harry Potter?

Albus Dumbledore founded the Order of the Phoenix in Harry Potter.

The Order of the Phoenix is a secret organization created by Dumbledore to oppose Lord Voldemort and his followers. It first operated during the First Wizarding War, when Voldemort rose to power, and was re-formed after Voldemort’s return near the end of Harry Potter and the Goblet of Fire.

Members include experienced witches and wizards such as Sirius Black, Remus Lupin, Mad-Eye Moody, and members of the Weasley family. The organization uses a headquarters at 12 Grimmauld Place during the later conflict. Its members carry out protective, intelligence, and resistance work rather than serving as an official government force.

The group is different from Dumbledore’s Army, which Harry, Ron, and Hermione help organize at Hogwarts. Dumbledore’s Army is a student-led practice group formed in Harry Potter and the Order of the Phoenix, while the Order of the Phoenix is an older resistance organization led by Dumbledore.