Fisting—also known as fist fucking (FF) and handballing—is a sexual activity that involves inserting one or more hands into the rectum (anal fisting) or the vagina (vaginal fisting). Fisting may be performed on oneself (self-fisting) or performed on one person by another. People who engage in fisting are often called "fisters".

Fisters have developed a distinct subculture with its own history, norms, and values, including literature and clubs for sexual, social, and spiritual exploration.