Keir David Peters Gilchrist (born September 28, 1992) is a Canadian actor and musician. On television, he played Marshall Gregson in the Showtime comedy-drama United States of Tara (2009–2011) and the lead role in 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). In addition to his acting career, Gilchrist is the vocalist of the grindcore band Whelm and the death metal band Phalanx.