What is the name of the film that marked Scorsese's directorial debut?

The film that marked Martin Scorsese’s directorial debut was Who’s That Knocking at My Door.

Released in 1967, the independent drama stars Harvey Keitel as J.R., a young Italian-American man in New York whose Catholic beliefs and traditional expectations are challenged when his girlfriend reveals that she was raped. The film explores guilt, masculinity, sexuality, friendship, and the pressures of cultural identity—subjects that would recur throughout Scorsese’s career.

The project began as a student film and changed titles and shape during production. It was initially called I Call First, and Scorsese later combined earlier footage about J.R. and his friends with a newly developed romantic storyline. His former professor Haig Manoogian helped finance and encourage the production.

Who’s That Knocking at My Door is Scorsese’s feature-film directorial debut; he had already made student shorts and other early film work. That distinction explains why The Big Shave, a 1967 short film directed by Scorsese, is not the best answer to this question. Harvey Keitel also made his acting debut in the film.