William Klein (born April 19, 1928) is an American-born French photographer and filmmaker noted for his ironic approach to both media and his extensive use of unusual photographic techniques in the context of photojournalism and fashion photography. He was ranked 25th on Professional Photographer's list of 100 most influential photographers.

Klein trained as a painter, studying under Fernand Léger and found early success with exhibitions of his work. He soon moved on to photography and achieved widespread fame as a fashion photographer for Vogue and for his photo essays on various cities. He has directed feature-length fiction films, numerous short and feature-length documentaries and has produced over 250 television commercials.

He has been awarded the Prix Nadar in 1957, the Royal Photographic Society's Centenary Medal and Honorary Fellowship (HonFRPS) in 1999, and the Outstanding Contribution to Photography Award at the Sony World Photography Awards in 2012.