María de Lourdes "Mia" Villiers Farrow (born February 9, 1945) is an American actress, activist, and former fashion model. She first gained notice for her role as Allison MacKenzie in the television soap opera Peyton Place and gained further recognition for her subsequent short-lived marriage to Frank Sinatra. An early film role, as Rosemary in Roman Polanski's Rosemary's Baby (1968), saw her nominated for a BAFTA Award and a Golden Globe Award for Best Actress. She went on to appear in several films throughout the 1970s, such as Follow Me! (1972), The Great Gatsby (1974), and Death on the Nile (1978). Her younger sister is Prudence Farrow.

Farrow was in a relationship with actor-director Woody Allen from 1980 to 1992 and appeared in thirteen of his fourteen films over that period, including Zelig (1983), Broadway Danny Rose (1984), The Purple Rose of Cairo (1985), Hannah and Her Sisters (1986), Radio Days (1987), Crimes and Misdemeanors (1989), Alice (1990), and Husbands and Wives (1992). Her later film roles include Widows' Peak (1994), The Omen (2006), Be Kind Rewind (2008), Dark Horse (2011), and Luc Besson's Arthur series (2006–2010).

Farrow has appeared in more than 50 films and won numerous awards, including a Golden Globe Award and three BAFTA Award nominations. Farrow is also known for her extensive work as a UNICEF Goodwill Ambassador. She is involved in humanitarian activities in Darfur, Chad, and the Central African Republic. In 2008, Time magazine named her one of the most influential people in the world.