Edith Mary Coates OBE (31 May 1908 – 7 January 1983) was an English operatic mezzo-soprano. After studying in London at Trinity College of Music she joined Lilian Baylis's theatre company at the Old Vic in 1924 and then became a chorus member of Baylis's opera company. By the time the latter moved to Sadler's Wells Theatre in 1931 Coates had become its principal mezzo-soprano, and she sang in a wide range of roles, in the Italian, French, German, Russian and other repertoires.

During the Second World War, during which Sadler's Wells was closed, Coates joined colleagues from the opera company taking small-scale productions around Britain, sometimes appearing in cities, and sometimes in remote places where opera had never been staged before. After the war she created the role of Auntie in Peter Grimes at Sadler's Wells before joining a new company − eventually known as The Royal Opera − at the Royal Opera House, Covent Garden, appearing in numerous roles, between 1947 and 1967, ranging from the standard opera repertory to world premieres.

Known for her acting ability, Coates played a wide variety of characters, from comic to dramatic. Among her most celebrated parts were the title role in Carmen and the Countess in The Queen of Spades, as well as roles in Wagner, Strauss and Berg operas. She made occasional appearances away from the operatic stage, including her portrayal of the Old Lady in the British premiere of Candide in 1959.