Mary Louise Weller (October 2, 1946 — October 1, 2026) was an American actress and model, who made her film debut with an uncredited minor role in Serpico (1973). Weller was especially memorable as a beautiful marine biologist in the made-for-TV Hunters of the Reef (1978) and, likewise, as professor Andrew Prine's college student lover in The Evil (1978). Her best known role was the snooty and uptight sorority snob Mandy Pepperidge in Animal House (1978). She went on to play the sole non-suicidal character in The Bell Jar (1979), Martin Kove's fetching wife in Blood Tide (1982), Chuck Norris' girlfriend in Forced Vengeance (1982) and a small part in Larry Cohen's Q (1982).

On TV, Weller had guest spots on a variety of 1970s network series. She voluntarily quit acting in the early 80s, and acted in a bunch of plays in New York and wrote the play Four Alone, which was performed at the Greenhouse Theater in Pasadena.

Moreover, Weller trained with the U.S. Equestrian Team as a teenager and has participated in horse-riding competitions. Weller unsuccessfully lobbied to get a film made, based on her own original script made about jockey Mary Bacon. She's a first cousin to writer Sheila Weller. In 1986, Weller purchased a large three-acre ranch in Malibu, California so she could raise horses.