York was born as Susannah Yolande Fletcher in London. York studied at the Royal Academy of Dramatic Art in London

York is probably best known for her part as Sophie Weston opposite Albert Finney in the 1963 Oscar winning Best Film Tom Jones. She is better known to younger audiences, however for playing Superman's mother Lara in Superman (1978) and its sequels, Superman II (1980) and Superman IV: The Quest for Peace (1987).

Her film career began in 1960. York appeared in Tunes of Glory, co-starring with Alec Guinness and John Mills. After Tom Jones, she appeared in the films A Man for All Seasons (1966), The Killing of Sister George (1968) and Battle of Britain (1969).

She was nominated for a Best Supporting Actress Oscar for They Shoot Horses, Don't They? (1969). She famously snubbed the Academy Awards when, regarding her nomination, she declared it offended her to be nominated without being asked. She did not attend the ceremony and lost to Goldie Hawn for her role in Cactus Flower.

In 1972 she won the Best Actress award at the Cannes Film Festival for her role in Images.

Her writing career is less well-known. In the 1970s she wrote two children's fantasy novels, In Search of Unicorns (1973), revised (1984) which was excerpted in the film Images, and Lark's Castle (1976, revised 1986).

In 1978, York appeared on stage at the New End Theater in London in The Singular Life of Albert Nobbs with Lucinda Childs, directed by French director Simone Benmussa.

Next year, she appeared in Paris, speaking French in a play by Henry James: Appearances, with Sami Frey. The play was again directed by Simone Benmussa.

In the 80's, again with Benmussa, York played in For no good Reason, an adaptation of George Moore's short story, with Susan Hampshire.

In 2007, she appeared in the UK tour of The Wings of the Dove, and continued performing her internationally acclaimed solo show, The Loves of Shakespeare's Women. Also in 2007, she guest starred in the Doctor Who audio play Valhalla.

In 2008 she played the part of Nelly in an adaptation of Wuthering Heights by April De Angelis.

York, according to Italian symphonic metal band Rhapsody of Fire website (previously known as Rhapsody), has been recruited for a narrated part on the band's next full-length album Triumph or Agony, which will also include Christopher Lee to return as the Wizard King.