He was the son of Porphyrian, and was born in Rome. Soon after he was elected pope, he was forced into exile due to the persecution of Emperor Gallus (251-253). The next emperor, Valerian (253-260) was at first more tolerant of Christians, and Lucius was therefore soon able to return, as were numerous other Christians who has chosen exile.
Little is known about his papacy. One of St Cyprian's letters indicate that he continued Pope Cornelius' practice of allowing lapsed Christians to return to the church. This question was debated intensely at the time; some felt that those who fell away from the church in the face of persecution should never be allowed back, while others felt that it was right that they should do penance and then return to the flock. St Cyprian one of the foremost advocates of the latter view.
He died early in March 254, of unknown causes. Tradition claims that he was martyred in the persecution of Valerian (who was tolerant at first, but then changed his mind), but this seems unlikely as the persecution had not started at that date.
He was buried in the Chamber of the Popes in the Catacombe di San Callisto, where part of the funerary inscription has been preserved. Later, when relics were brought to safety within the city walls, his mortal remains were brought to Santa Cecilia in Trastevere. Many relics were sent to other churches; one of the most precious is his head, which was brought to Roskilde in Denmark c. 1100. St Lucius had been made patron of the church and of the Danish region Zealand. The relic survived the Reformation, and is today exhibited in St Ansgar Catholic Cathedral in Copenhagen.