Lucius of Britain was a legendary monarch of the Britons during the 2nd century. He is traditionally credited with introducing Christianity to his people after requesting to convert through a letter sent to Pope Eleutherius. While his historical existence is debated by scholars, who suggest he may be a legendary figure or a misidentification of an Edessan ruler, he remains a significant figure in British Christian tradition. He is commemorated as a saint in various traditions, with his feast day observed on 3 December.