Dame Margaret Natalie Smith, (born 28 December 1934) is an English actress. She has had an extensive, varied career on stage, film and television spanning over 66 years. Smith has appeared in over 50 films and is one of Britain's most recognizable actresses. A prominent figure in British culture for six decades, she was made a Dame by Queen Elizabeth II in 1990 for services to the performing arts, and received the Companion of Honour from the Queen in 2014 for services to drama.

Smith began her career on stage as a student performing at the Oxford Playhouse in 1952 and made her professional debut on Broadway in New Faces of '56. For her work on the London stage, she has won a record five Best Actress Evening Standard Awards; for The Private Ear and The Public Eye (both 1962), Hedda Gabler (1970), Virginia (1981), The Way of the World (1984) and Three Tall Women (1994). She received Tony Award nominations for Private Lives (1975) and Night and Day (1979), before winning the 1990 Tony Award for Best Actress in a Play for Lettice and Lovage. Other stage roles include Stratford Shakespeare Festival productions of Antony and Cleopatra (1976) and Macbeth (1978), and West End productions of A Delicate Balance (1997) and The Breath of Life (2002).

On screen, Smith first drew praise for the crime film Nowhere to Go (1958), for which she received her first BAFTA Award nomination. She has won two Academy Awards, winning Best Actress for The Prime of Miss Jean Brodie (1969) and Best Supporting Actress for California Suite (1978). She is one of only six actresses to have won in both categories. She has won a record four BAFTA Awards for Best Actress, including for A Private Function (1984) and The Lonely Passion of Judith Hearne (1988), a BAFTA for Best Supporting Actress for Tea With Mussolini (1999), and three Golden Globe Awards. A six-time Oscar nominee, her other nominations were for Othello (1965), Travels with My Aunt (1972), A Room with a View (1986), and Gosford Park (2001).

Smith played Professor Minerva McGonagall in the Harry Potter film series (2001–11). Other notable films include Love and Pain and the Whole Damn Thing (1973), Death on the Nile (1978), Clash of the Titans (1981), Evil Under the Sun (1982), Hook (1991), Sister Act (1992), The Secret Garden (1993), The Best Exotic Marigold Hotel (2012) and The Lady in the Van (2015). She won an Emmy Award in 2003 for My House in Umbria, to become one of the few actresses to have achieved the Triple Crown of Acting, and starred as Lady Violet Crawley, Dowager Countess of Grantham on Downton Abbey (2010–15), for which she won three Emmys, her first non-ensemble Screen Actors Guild Award and her third Golden Globe. Her honorary awards include the BAFTA Special Award in 1993, the BAFTA Fellowship in 1996, and the Special Olivier Award in 2011. She received the Stratford Shakespeare Festival's Legacy Award in 2012, and the Bodley Medal by the University of Oxford's Bodleian Libraries in 2016.