Caragh M. O'Brien is an American novelist, best known as the author of the Birthmarked trilogy, a series of young adult, dystopian novels. Her books take place in a world destroyed by climate change. O'Brien is also known for her adult novel, Annie Bot, about a malfunctioning gynoid companion, which she wrote under the pen name Sierra Greer.

Born in St. Paul, Minnesota, Ms. O'Brien earned her BA from Williams College and her MA from Johns Hopkins University. Once a high school English teacher, she resigned to write young adult novels. For more information, visit her website.