Joan Didion (born December 5, 1934) is an American writer, renowned as a journalist and prose stylist. Didion contributes regularly to The New York Review of Books and The New Yorker. With her late husband, writer John Gregory Dunne, she collaborated on several screenplays. She lives in New York City.

Didoin was born in Sacramento, California and graduated from the University of California at Berkeley in 1956. Much of Didion's writing has focused on California, particularly the 1960s and the passing of the world that she grew up in. Her portrayals of Charles Manson, conspiracy theorists, paranoiacs, and sociopaths is now considered part of American Literature.

Didion is the author of five novels and seven books of non-fiction. Her collections of essays, Slouching Toward Bethlehem (1968) and The White Album (1979) -- a book described in one review as helping to define California as "the paranoia capital of the world" -- made her a famous observer of American politics and culture with a distinctive style of reportage that mixed personal reflection and social analysis. This led her to be associated with members of the New Journalism such as Tom Wolfe and Hunter S. Thompson, though Didion's ties to that movement have never been considered particularly strong.

Didion's most recent book Where I Was From (2003) is considered to be the most autobiographical of her works. It contains both new and collected essays, all of them reflections on California mythologies, and on the author's somewhat complicated relationship to her birth place and her mother. Indirectly it also serves as a rumination on the American frontier myth and the rootless, consumerist lifestyle that California can be said to have pioneered.

Didion has one child, a daughter, Quintana Roo Dunne, who was adopted at birth.