Which Hogwarts subject does Remus Lupin teach while he is a professor?

Remus Lupin teaches Defence Against the Dark Arts during his year as a Hogwarts professor.

Lupin appears as the subject's teacher in Harry Potter and the Prisoner of Azkaban. Unlike several other instructors who hold the post, he is respected by students for his calm manner, practical lessons, and ability to explain dangerous magical creatures clearly.

His classroom teaching includes a memorable lesson about the boggart, a shape-shifting creature that takes the form of a person's greatest fear. Lupin also helps Harry learn the Patronus Charm, which becomes an important protection against Dementors.

Lupin leaves Hogwarts at the end of the school year after his werewolf identity becomes known. The post's repeated staff changes are linked to a long-standing curse described in the series, making Defence Against the Dark Arts one of the school's most unstable subjects.