Keir David Peters Gilchrist (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.