Theresa Lynn Russell (née Paup; born March 20, 1957) is an American actress whose career spans over four decades. Her filmography includes over 50 feature films, ranging from mainstream to independent and experimental films.

Born in San Diego, Russell was raised in the Los Angeles suburb of Burbank, where she had a turbulent upbringing marked by poverty, and dropped out of high school at age 16. Russell subsequently began modeling, which brought her to the attention of film producer Sam Spiegel. Through Spiegel, she was cast in Elia Kazan's The Last Tycoon (1976), playing the daughter of a prominent film executive.

In 1978, Russell starred opposite Dustin Hoffman in the critically-acclaimed crime drama Straight Time. Her next role was a lead in English filmmaker Nicolas Roeg's controversial thriller Bad Timing (1980), which earned critical praise. Russell and Roeg began a romance while shooting the film, and it marked one of six projects they would collaborate on following their 1982 marriage. She next appeared in Roeg's drama Eureka (1983), followed by the John Byrum-directed The Razor's Edge (1984). Russell portrayed Marilyn Monroe in Roeg's experimental alternate history film Insignificance (1985), followed by a lead role as a serial killer in Bob Rafelson's neo-noir film Black Widow (1987), which garnered her significant commercial attention.

Russell continued to collaborate with Roeg throughout the late 1980s and early 1990s, appearing in a Roeg-directed segment of the anthology film Aria (1987), as well as the features Track 29 (1989) and Cold Heaven (1991). Other roles from this time included the crime dramas Physical Evidence (1989) and Impulse (1990).

In 1991, Russell starred as a prostitute in Ken Russell's satirical drama Whore, followed by Steven Soderbergh's experimental black-and-white feature, Kafka, co-starring Jeremy Irons. After appearing in a number of independent films in the mid-1990s, Russell had a supporting role in the commercially successful neo-noir Wild Things (1998), and the critically-acclaimed drama The Believer (2001). In 2005, she had a supporting role on the HBO miniseries Empire Falls, followed by a minor part in Sam Raimi's Spider-Man 3 (2007).

The song "Athena" by the rock group The Who, was written about a 1979 chance meeting with Pete Townshend, who was smitten and rejected by her. The single appears on the band's 1982 album, It's Hard.