Leif Hans Larsen Tronstad DSO, OBE (27 March 1903 – 11 March 1945) was a Norwegian scientist, intelligence officer and military organizer. He graduated from the Norwegian Institute of Technology in 1927 and was a prolific researcher and writer of academic publications. A professor of chemistry at the Norwegian Institute of Technology from 1936, he was also among the pioneers of heavy water research, and was instrumental when a heavy water plant was built at Vemork.