Kristofer Siimar (born 3 February 1998) is an Estonian tennis player.

Siimar has a career high ATP doubles ranking of 1276 achieved on 13 August 2018.

[1] Siimar represents Estonia at the Davis Cup where he has a W/L record of 0–1.

His twin brother Mattias Siimar is also a tennis player.

This biographical article relating to Estonian tennis is a stub.