Saint Laurence was one of the seven deacons martyred during the persecution of the Emperor Valerian in 258. 10 August is his feast day. The breviary entry about him says:
Laurence was one of the seven deacons of the Church of Rome and was executed on 10th August 258, four days after Sixtus II and his companions. By now, few of the facts of his life are known for certain: he was probably a Spaniard from Toledo.
A basilica was built over Laurence’s tomb fifty years after his death, by the Emperor Constantine, and the anniversary of his martyrdom was kept as a solemn feast – with considerably more solemnity than that of Pope Sixtus II (we do not know why). By the sixth century, it was one of the most important feasts throughout much of western Christendom. His name occurs (with Sixtus’s) in the Roman Canon of the Mass.