Kai Gudbrand Grjotheim (13 July 1919 – 17 April 2003) was a Norwegian chemist. He was born in Åsnes as a son of school manager Erland Gudbrandson Grjotheim (1887–1969) and domestic science teacher Kaya Johanne Haarbye (1882–1963). He was married to Jorunn Synnøve Andersen since 1944. He finished his secondary education at Hamar Cathedral School in 1940, graduated from the Norwegian Institute of Technology with the siv.ing. degree in 1950. He was a research fellow from 1952 to 1955 and docent from 1955 to 1956 and 1957 to 1959. In 1956 he took the degree on the thesis Contribution to the Theory of the Aluminum Electrolysis, and from 1956 to 1957 he did research at the University of Toronto.