Armando Dippet was Hogwarts headmaster immediately before Albus Dumbledore in J.K. Rowling’s Harry Potter books.
Dippet is seen mainly through memories and historical references rather than as a major present-day character. He was headmaster during Tom Riddle’s time at Hogwarts, when the Chamber of Secrets was opened and a student, Myrtle Warren, was killed.
Riddle manipulated the circumstances so that the school blamed the attacks on the giant spider Aragog. Dippet accepted the explanation and considered closing Hogwarts, but Riddle’s account helped prevent the school from being permanently shut.
Dumbledore later succeeded Dippet as headmaster. This makes Dippet distinct from Phineas Nigellus Black, another former headmaster whose portrait appears in the books, and from Minerva McGonagall, who served as headmistress after Dumbledore’s era.