Karol Sikora (born 17 June 1948) is a British physician specialising in oncology, who has been described as a leading world authority on cancer. He is a founder and medical director of Rutherford Health, a company providing proton therapy services, and Director of Medical Oncology at the Bahamas Cancer Centre. He is currently Professor of Medicine at the University of Buckingham, and a partner in and dean of Buckingham's medical school.