The Best Original Screenplay category honours work that is not based on previously published material. The category was first introduced in 1940. Prior to that original screenplays were included in the Best Story category and in 1957 the two categories were merged once again, this time under the Original Screenplay moniker.
This year's nominees:
Mark Boal, Hurt Locker: Boal has been nominated for the WGA, BAFTA, Critics Choice and Golden Globe awards, and won the Chicago Film Critics Award for his screenplay. He also won the PGA as one of The Hurt Locker's producers. This is his first nomination.
Quentin Tarantino, Inglorious Basterds: This is Tarantino's second Oscar nomination for screenplay, the first coming for Pulp Fiction. He won the Critics Choice Award and received nominations from the Golden Globes and BAFTAs. He was not eligible for a WGA nomination.
Alessandro Camon & Oren Moverman, The Messenger: Known primarily as a producer, Camon's credits as a writer are few. Moverman's credits include Jesus' Son, I'm Not There and Married Life. This is the first Oscar nomination for both.
Joel & Ethan Coen, A Serious Man: The Coen brothers have three previous screenplay nominations (seems like it ought to be more, eh?) for O Brother Where Art Thou?, and for Fargo and No Country For Old Men, both of which they won. Their screenplay for A Serious Man has received nominations from the WGA and won the National Society of Film Critics Award and National Board of Review Award.
Bob Peterson, Pete Doctor & Thomas McCarthy, Up: This is the second nomination for Peterson (previous for Finding Nemo), the third writing nomination for Stanton (Wall-E, Toy Story) and the first nomination for McCarthy. The screenplay has received Annie, BAFTA and Critics Choice nominations.