Kristoffer Ajer (born 17 April 1998) is a Norwegian footballer who plays as a defensive midfielder for Celtic.
Started his career with Rælingen FK before joining Lillestrøm when he was 10-years-old.
Moved to Start 2014.
Made his first team debut in July 2014 against Bodø/Glimt.
Named captain against former youth club Lillestrøm in April 2015 at just 16-years-old, becoming the youngest ever footballer to captain a team in the Tippeligaen.
Had a one-week trail with Celtic in January 2016, signing a four-year deal the following month.
Joined Kilmarnock on a six-month loan deal in January 2016.
Returned to Celtic after playing 17 first team games.
Has represented Norway at every level from Under-16 to Under-21.
Made his senior Norwary debut in March 2018.