Usha Ranjan Ghatak (1931–2005) was an Indian synthetic organic chemist, stereochemist and the director of the Indian Association for the Cultivation of Science (IACS). He was known for his contributions in developing novel protocols of stereoselective synthesis of diterpenoids. He was an elected fellow of the Indian Academy of Sciences and the Indian National Science Academy. The Council of Scientific and Industrial Research, the apex agency of the Government of India for scientific research, awarded him the Shanti Swarup Bhatnagar Prize for Science and Technology, one of the highest Indian science awards, in 1974, for his contributions to chemical sciences.