Daniel Gideon Mazer (born 4 October 1971) is a British director, screenwriter, producer, and comedian. He is best known as comedian Sacha Baron Cohen's long-time writing and production partner, who worked with him on his three unorthodox characters Ali G, Borat, and Brüno. He also co-wrote and co-produced films based on Baron Cohen's characters, such as Ali G Indahouse, Borat, and Brüno.

Mazer attended The Haberdashers' Aske's Boys' School, where he met Baron Cohen. He then read Law at Peterhouse, Cambridge University, and graduated in 1994. While at university, he was an active member of Cambridge Footlights and was vice president from 1993 to 1994.