Has anyone ever been awarded the Nobel Prize in Literature posthumously and if so who when?

Yes, the Nobel Prize in Literature has been awarded posthumously on several occasions. Here are a few examples:

- Erik Axel Karlfeldt (Swedish poet and novelist) in 1931

- Eugene O'Neill (American playwright) in 1936

- Gabriela Mistral (Chilean poet-diplomat) in 1945

- Albert Camus (French Algerian novelist) in 1957

- Dag Hammarskjöld (Swedish diplomat) in 1961

- Jean-Paul Sartre (French existentialist philosopher, playwright) in 1964 (declined the prize)

- Eyvind Johnson (Swedish novelist) in 1974 (joint recipient)

- Harry Martinson (Swedish poet, author) in 1974 (joint recipient)

- Odysseus Elytis (Greek poet) in 1979