Albus Dumbledore is the Hogwarts headmaster who precedes Severus Snape in J.K. Rowling's Harry Potter series.
Dumbledore serves as headmaster for most of the main story and is one of the wizarding world's most powerful and influential figures. He is portrayed as a mentor to Harry, although important parts of his past and plans are deliberately withheld from the young wizard for much of the narrative.
Severus Snape becomes headmaster during the events of Harry Potter and the Deathly Hallows, after the previous leadership of Hogwarts changes during the conflict with Voldemort. Minerva McGonagall later leads the school after the battle, so she is not the answer to this question either.
Dumbledore's full name is Albus Percival Wulfric Brian Dumbledore. His earlier history includes his friendship and later conflict with Gellert Grindelwald, a major element explored in the later Wizarding World film series.