Date of birth unknown; elected 30 June, 296; died 304.
Born in Rome (date unknown); died there on October 25, 304, his second feast day; He may have died a martyr's death by beheading, but this is still very uncertain;
Marcellinus' pontificate began at a time when Diocletian was Roman Emperor, but had not yet started to persecute the Christians. He left Christianity rather free and so the church's membership grew. Caesar Galerius led the pagan movement against Christianity and arrived to bring up Diocletian against Christianity in the year 302: First Christian soldiers had to leave the army, later the Church's property was confiscated and Christian books were destroyed. After two fires in Diocletian's palace he took harder measures against Christians: they had either to apostatize or they were sentenced to death.
St. Marcellinus was a Roman, the son of Projectus. When he first became pope, Diocletian was already Emperor, but he had not yet drawn the sword against the Christians. At first under the influence of his wife, Prisca, and his daughter, Valeria, Diocletian left the Christians fairly free. The peace, however, had caused Christianity to grow and grow. This provoked a fierce reaction among the pagans whose leader was the Caesar Galerius.
According to Lactantius, the historian of the persecution, Diocletian was first angered by the Christians when the augurs or soothsayers told him that they could not prophesy because Christians made the sign of the cross. The Emperor promptly ordered all Christians to apostatize or get out of the army. This was in 302. The next year at a conference in Nicomedia, Galerius urged the Emperor to extend himself against the Christians. Diocletian asked the opinion of the oracle of Apollo at Miletus. The oracle indicated the Christians interfered with his ability to properly assist. Diocletian started his persecutions by ordering the confiscation of Church property and the destruction of Christian books. When a rash Christian actually tore down the imperial edict right under the imperial nose at Nicomedia and two very convenient fires broke out in the imperial palace, Diocletian, enraged, ordered Christians reject their faith, worship the pagan gods, or die. The deaths were too numerous to number.
The persecution hit Rome with disastrous results for the historians. The papal archives were seized and destroyed. The famous Cemetery of Calixtus was saved by the Christians, who blocked up the entrance.
Pope St. Marcellinus was accused by Donatist heretics of having handed over the sacred books. Some went so far as to accuse him of having sacrificed to idols. The Liber Pontificalis repeats this but adds that St. Marcellinus repented and died a martyr. These accounts were later proven to be false, and St. Augustine denies openly that the Pope had weakened.
At any rate, St. Marcellinus did die a confessor of Christ in 304. According to the Liber Pontificalis, after his head was cut off, his body, along with those of other martyrs, was left lying on the street for twenty- six days to terrify the Christians. Then a priest buried the Pope in the Cemetery of Priscilla, on the Via Salaria.
After a considerable interregnum he was succeeded by Marcellus, with whom he has sometimes been confused. During his pontificate, Armenia became the first Christian nation in 301.