Mary Tamm (born 22 March 1950 in Dewsbury, West Yorkshire) is an English actress of Estonian descent, perhaps best known for being the first actress to play the character of Romana in the science fiction television series Doctor Who, opposite Tom Baker as the Doctor, from the 1978 - 1979 season known collectively as The Key to Time. She is a graduate and an associate member of the Royal Academy of Dramatic Art.

She began her acting career on the stage with the Birmingham Repertory Company in 1971, moving to London in 1972 and appearing in the musical Mother Earth. Before her association with Doctor Who, Tamm acted in several motion pictures, most notably The Odessa File (1974) and The Likely Lads (1976).

Tamm was not initially interested in playing a companion to the Doctor as she believed that the role was merely that of the "damsel in distress". However, she changed her mind when assured by the producers that Romana would be different. Romana was supposed to be a Time Lady, a member of the Doctor's own people and therefore as capable as the Doctor. She left the programme after only one season as she was unhappy about the limited nature of the character. The role of Romana was assumed by Lalla Ward.

Since then, Tamm has acted in both film and television, playing the characters of Penny Crosbie in the soap opera Brookside from 1993 to 1995, Yvonne Edwards in the BBC drama Paradise Heights (2002), as well as guest roles in many other television programmes. Tamm returned to the role of Romana in the second series of Gallifrey audio plays produced by Big Finish Productions. Her first appearance in these was in Gallifrey: Lies (2005).

She married Marcus Ringrose in 1978. They have one daughter and a grandson.

Graduated from RADA.

Became an associate member of RADA, and joined the associate's committee.