Nolan beat such contenders as "Black Swan" (screenplay by Mark Heyman and Andres Heinz and John McLaughlin; story by Andres Heinz); "The Fighter" (screenplay by Scott Silver and Paul Tamasy & Eric Johnson; story by Keith Dorrington & Paul Tamasy & Eric Johnson); "The Kids Are All Right" by Lisa Cholodenko & Stuart Blumberg; and Nicole Holofcener's "Please Give."
Aaron Sorkin's script for "The Social Network," adapted from Ben Mezrich's book "The Accidental Billionaires," won Best Adapted Screenplay.
Sorkin has won numerous' critics awards, including the Golden Globe, for his examination of the creation of Facebook.
Other nominees in the Adapted Screenplay category were "127 Hours" (screenplay by Danny Boyle & Simon Beaufoy, based on the book "Between a Rock and a Hard Place" by Aron Ralston); "I Love You Phillip Morris" (John Requa & Glenn Ficarra, based on the book by Steven McVicker); "The Town" (screenplay by Peter Craig and Ben Affleck & Aaron Stockard, based on the novel "Prince of Thieves" by Chuck Hogan) and Joel & Ethan Coen for "True Grit," based on novel by Charles Portis.
Charles Ferguson, Chad Beck and Adam Bolt were awarded the documentary screenplay award for "Inside Job," about the 2008 collapse of the financial sector.
A few fellow Oscar contenders in the screenplay categories, including David Seidler's original script for "The King's Speech," Michael Arndt's "Toy Story 3," and Debra Granik and Anne Rosellini's "Winter's Bone," were not nominated, being ineligible under the writing union's contract guidelines.
Recipients of honorary awards at Saturday's ceremony include Steve Zaillian ("Schindler's List"); writer-producer Diane English ("Murphy Brown"); Mike Scully ("The Simpsons") ; Jez Butterworth & John-Henry Butterworth ("Fair Games"); Tonino Guerra ("Blow-Up"); Seth Freeman ("Lou Grant"); and Susannah Grant ("Erin Brockovich").