Which Hogwarts subject does J.K. Rowling’s character Remus Lupin teach?

J.K. Rowling’s character Remus Lupin teaches Defence Against the Dark Arts at Hogwarts.

Lupin is the Defence Against the Dark Arts professor in Harry Potter and the Prisoner of Azkaban, the third main novel. He is presented as a knowledgeable and unusually effective teacher who gives students practical experience with magical threats, including the Boggart lesson.

His teaching role is especially important because the subject has a reputation for instability. In the earlier books, Hogwarts has different Defence Against the Dark Arts professors, and the position does not remain permanently occupied by one teacher during Harry’s education. Lupin eventually leaves Hogwarts after his lycanthropy becomes public.

Lupin is also a former member of the original Order of the Phoenix and a school friend of Harry’s parents. Those facts add personal context to his relationship with Harry, but they do not change his Hogwarts subject: his teaching post is Defence Against the Dark Arts.