Ursicinus, also known as Ursinus, was elected pope in a violently contested election in 366 as a rival to Pope Damasus I. He ruled in Rome for several months in 366 – 367, was afterwards declared an antipope, and died after 381. Pope Liberius had been banished in 355, as a result of a conflict with the Emperor Constantius II over the treatment of Arianism. Antipope Felix II was imposed as his successor. After the Emperor's death, Liberius was eventually reinstalled and Felix expelled from Rome. The rival parties remained highly polarized in Rome, however.