Sierra McCormick (born October 28, 1997) is an American actress. She first became known for participating on the game show Are You Smarter Than a 5th Grader? (2007–2008) before shifting her focus onto acting, receiving attention for portraying Lilith on the television series Supernatural (2008). She then starred as Scout Thomas on the comedy television series Romantically Challenged (2010), and as Olive Doyle on the Disney Channel series A.N.T. Farm from 2011 to 2014.
McCormick made her film debut starring as Susan Kushner in the comedy film Ramona and Beezus (2010), and has since voiced Alice in the direct-to-DVD film Spooky Buddies (2011), starred as Moira in the indie film Some Kind of Hate (2015), and co-starred as Fay Crocker in the science fiction film The Vast of Night (2019).