Thomas J. Kelly is an American cancer researcher whose work focuses on the molecular mechanisms of DNA replication. Kelly is director of the Sloan-Kettering Institute, the basic research arm of the Memorial Sloan-Kettering Cancer Center. He holds the Center's Benno C. Schmidt Chair of Cancer Research. Before joining Sloan-Kettering in 2002, Kelly was professor and director of the Department of Molecular Biology and Genetics at the Johns Hopkins University School of Medicine and was the founding director of the Johns Hopkins Institute for Basic Biomedical Sciences.