Kai Kristiansen (born 1929) is a Danish furniture designer.
Kai Kristiansen was apprenticed as a cabinetmaker in 1949, after which he studied at the Royal Danish Academy of Fine Arts under Kaare Klint. He started his own design studio in 1955, where he collaborated with many Danish furniture manufacturers.
Some of Kristiansen’s most famous furniture are the chairs Model 42 (Z-chair), Model 31, Model 121 (lounge chair) and the shelf FM Reolsystem.