The Ghost Sonata (Swedish: Spöksonaten) is a play in three acts by the Swedish playwright August Strindberg. Written in 1907, it was first produced at Strindberg's Intimate Theatre in Stockholm on 21 January 1908. Since then, it has been staged by such notable directors as Max Reinhardt, Olof Molander, Roger Blin, and Ingmar Bergman. Bergman directed it four times: in 1941, 1954, 1973, and 2000. Strindberg took the title from Beethoven's Piano Sonata No. 17 in D minor, which he called 'The Gespenster Sonata', and also Piano Trio No. 4 in D major, known as the 'Ghost Trio'.
The Ghost Sonata is a key text in the development of modernist drama and a vivid example of a chamber play. In it, Strindberg creates a world in which ghosts walk in bright daylight, a beautiful woman is transformed into a mummy and lives in the closet, and the household cook sucks all the nourishment out of the food before she serves it to her masters.