Lloyd Mayer (June 21, 1952 – September 5, 2013) was an American gastroenterologist and immunologist. He was Professor and Co-Director of the Immunology institute at the Mount Sinai Medical Center, now known as the Lloyd Mayer Immunology Institute. Mayer was Professor and Co-Director of the Immunology institute at the Mount Sinai Medical Center and the Dorothy and David Merksamer Professor of Medicine, as well as Professor of Microbiology at the Mount Sinai School of Medicine. Dr. Mayer died following a three-year battle with brain cancer (Glioblastoma) in September 2013.