Jean Lyndsey Torren Marsh (1 July 1934 – 13 April 2025) was an English actress and writer. She co-created and starred in the ITV series Upstairs, Downstairs (1971–1975), for which she won the 1975 Emmy Award for Outstanding Lead Actress in a Drama Series for her performance as Rose Buck. She reprised the role in the BBC's revival of the series (2010–2012).

Marsh co-created the television series The House of Eliott in 1991. Her film appearances include Cleopatra (1963), Frenzy (1972), The Eagle Has Landed (1976), The Changeling (1980), Return to Oz (1985), Willow (1988), Fatherland (1994) and Monarch (2000). She is also known for three roles in Doctor Who: as Joan of England in The Crusade; Sara Kingdom, a companion of the First Doctor; and a villain opposite the Seventh Doctor. From 1955 to 1960 she was married to Jon Pertwee, who played the Third Doctor in the series.

Marsh was born on 1 July 1934, and grew up in Stoke Newington, London, one of two daughters born to Henry and Emmeline (née Bexley) Marsh. She studied ballet, singing, and acting from an early age.

During the 1950s and 1960s, Marsh made many appearances on British and American television, including an episode of The Twilight Zone called "The Lonely" (1959), in which she portrayed a lifelike gynoid; The Moon and Sixpence (1959), opposite Laurence Olivier and Denholm Elliott; The Wonderful World of Disney (1961); an episode of the series Danger Man (1961), entitled "Name, Date and Place" as Kim Russell, Gideon's Way (1965); I Spy (1967); in four episodes of The Saint (1964–1968); and one episode of UFO ("Exposed" 1970, as Janna). She was also a regular alongside Ian Hendry in the ITV series The Informer (1966–67).

Marsh appeared several times in the BBC series Doctor Who. She first appeared alongside William Hartnell in the 1965 serial The Crusade as Lady Joanna, the sister of Richard I (The Lionheart). She returned later that year as companion Sara Kingdom in 9 episodes of the 12-part serial The Daleks' Master Plan. Marsh reprised the role in the audio plays Home Truths (2008), The Drowned World (2009), The Guardian of the Solar System (2010), The Five Companions (2011), The Anachronauts (2012), The Light At The End (2013), An Ordinary Life (2014) and The Sontarans (2016). She also appeared in the 1989 television serial Battlefield as Morgaine, as well as the 2007 audio play The Wishing Beast. She made an un-billed cameo appearance in the 2013 docudrama about Doctor Who, An Adventure in Space and Time.

Marsh featured as Bertha Mason Rochester in the George C. Scott-Susannah York version of Jane Eyre, directed by Delbert Mann. The film was released theatrically in the United Kingdom in 1970 and shown in the United States on NBC television in 1971.

Marsh's 2000 (re-released in cinemas in 2014) film about the death of Henry VIII, Monarch.

With Eileen Atkins, Marsh created the British period television drama Upstairs, Downstairs, and played the role of the house parlourmaid Rose Buck for the duration of the series, from 1971 until 1975. The programme was screened internationally and received numerous awards including two BAFTA Awards, two Royal Television Society awards, eight Emmys and a Golden Globe. Marsh received a Royal Television Society award in 1971 and an Emmy Award for Outstanding Lead Actress for her role in 1975, and was nominated for the same award on three more occasions – 1974, 1976, and (for the show's revival) in 2011. She also received awards from the American Drama Centre and American Drama Critics Circle for the role as well as two Golden Globe Award nominations.