Fabian was a Roman layman who came up from the countryside to attend the election of a new pope after the death of Pope Anterus in 236. As the crowd debated, a white dove came down and rested on his head. Taking this as a sign, the assembly acclaimed him bishop of Rome — the rare case of a saint elected by such public manifestation.
His pontificate (236–250) was a time of relative peace for the Roman Church. He divided Rome into seven deaconries (the precursor of today's deaneries), reorganized the catacombs of San Callisto, and built the burial monuments for previous popes. He is recorded as having sent missionaries to Gaul.
In December 249 the Emperor Decius issued his edict requiring every citizen to sacrifice to the Roman gods. Fabian refused. He was arrested and martyred on January 20, 250 — the first major Christian victim of the Decian persecution. His tomb in the Catacomb of San Callisto bears the simple Greek inscription: ΦΑΒΙΑΝΟC ΕΠΙ ΜΡ ('Fabian, Bishop, Martyr').