Mark and Marcellian
Roman martyrs venerated as saints
Feast: 18 June (1962 Missal, commemoration) · not on the current Roman calendar
Who they were
Mark and Marcellian were brothers martyred at Rome under Diocletian, probably in 286. According to the ancient Acts of St Sebastian, when they were in prison for the faith their pagan parents, Tranquillinus and Martia, begged them to sacrifice and save their lives; St Sebastian came and strengthened them so that they stood firm, and converted their parents too. Condemned, they were buried on the Via Ardeatina near the cemetery of Domitilla.
The miracles
There was never a formal cause: they have been honoured as martyrs since the early centuries. Their relics were later moved to Sts Cosmas and Damian in Rome, where they were found again in 1583.
Why that counted as sanctity
Two brothers, tempted by their parents' tears, held to Christ, and their faithfulness converted their family.
- Catholic Encyclopedia (1913), via New Advent - Sts. Mark and Marcellian
- Wikidata Q670905 — dates, feast day and identifiers (CC0)
- English Wikipedia — Mark and Marcellian (CC BY-SA)
Checked against the sources listed on 21 September 2026. Corrections welcome.