Louis J. Ignarro (born May 31, 1941) is an American pharmacologist. For demonstrating the signaling properties of nitric oxide, he was co-recipient of the 1998 Nobel Prize in Physiology or Medicine with Robert F. Furchgott and Ferid Murad.
Currently, he is professor of pharmacology at the UCLA School of Medicine’s department of molecular and medical pharmacology in Los Angeles, which he joined in 1985. Before relocating to California, he was a professor of pharmacology at Tulane University School of Medicine, New Orleans, for 12 years. Ignarro has also previously worked as a staff scientist, research department, for the pharmaceutical division of CIBA-GEIGY Corporation in New York.