Keir David Peters Gilchrist (/ˈkɪər ˈɡɪlkrɪst/; born 28 September 1992) is a Canadian actor and musician. On television, he portrayed Marshall Gregson on the Showtime comedy-drama United States of Tara (2009–2011) and headlined the Netflix comedy-drama Atypical (2017–2021). His film roles include the comedy-drama It's Kind of a Funny Story (2010) and the supernatural horror It Follows (2014). Outside of his acting career, Gilchrist is the vocalist of grindcore band Whelm and death metal band Phalanx.

Early life
Gilchrist was born in Camden Town, London, to Canadian parents Catherine (née Peters) and Ian Gilchrist. His maternal grandfather was banker, economist, and politician Douglas Peters, and his uncle is economist David Wilfrid Peters. Gilchrist spent his early years in London, before relocating to Boston, Massachusetts, during his childhood, then to New York City, before finally settling in Toronto, Ontario.