Dame Enid Diana Elizabeth Rigg, (born 20 July 1938) is an English actress. She is best known for playing Emma Peel in the 1960s TV series The Avengers (1965–68), and Olenna Tyrell in Game of Thrones (2013–17). She has also had an extensive career in theatre, including playing the title role in Medea, both in London and New York, for which she won the 1994 Tony Award for Best Actress in a Play. She was made a CBE in 1988 and a Dame in 1994 for services to drama.

Rigg made her professional stage debut in 1957 in The Caucasian Chalk Circle, and joined the Royal Shakespeare Company in 1959. She made her Broadway debut in the 1971 production of Abelard & Heloise. Her film roles include Helena in A Midsummer Night's Dream (1968); Countess Teresa di Vicenzo, wife of James Bond, in On Her Majesty's Secret Service (1969); Lady Holiday in The Great Muppet Caper (1981); and Arlena Marshall in Evil Under the Sun (1982). She won the BAFTA TV Award for Best Actress for the 1989 BBC miniseries Mother Love, and an Emmy Award for her role as Mrs. Danvers in the 1997 adaptation of Rebecca. Her other television credits include You, Me and the Apocalypse (2015), Detectorists (2015), and the Doctor Who episode "The Crimson Horror" (2013) opposite her daughter, Rachael Stirling.