Don H. Catlin (1938-2024) was an American scientist, considered one of the founding fathers of modern anti-doping science. His career is primarily associated with the 1982 founding of the UCLA Olympic Analytical Laboratory, the first accredited anti-doping laboratory in the United States, which he directed for 25 years. His work was crucial in developing innovative methodologies for the identification of doping substances. He is best remembered for his 2003 identification of the designer steroid tetrahydrogestrinone (THG), a discovery that initiated the BALCO scandal and revolutionized sports drug testing. After leaving UCLA, he founded non-profit organizations such as Anti-Doping Research, Inc. and the Banned Substances Control Group (BSCG) to continue research and certify supplements. For his fundamental contribution to sports integrity, Catlin received numerous awards from bodies such as the International Olympic Committee and the United States Olympic & Paralympic Committee.