Of all the Roman missionaries sent into Gaul, Saint Dionysius or Denys the Areopagite, converted by Saint Paul in Athens, carried the Faith farthest into the west, fixing his see at Paris. France claims him as one of her greatest glories.
He was a highly educated philosopher of Greece, and one of the nine archontes or leaders of the city of Athens, a counselor, as some say, if not the Head of the Athenian senate. He was born in the year 9 of the Christian era, and had traveled to Heliopolis in Egypt to learn mathematics and astrology. There he saw for himself, in his early twenties, the eclipse of the sun contrary to all the laws of nature, which occurred at the death of the Son of God. His teachers could not explain it to him otherwise than as a sign of changes in divine matters. In his letters to Saint Polycarp he says himself that the astrologer he questioned had answered him rather by divine inspiration than by any natural knowledge. And he himself had cried out: Either the God of nature is suffering, or the entire mechanism of the world is going to be destroyed to return to its ancient state of chaos! Already he was being prepared for his conversion twenty years later, which is related by Saint Luke in the Acts of the Apostles, chapter seven.
Through Saint Paul, the see of Athens was established with Saint Denys as its first bishop, and this flock, which he extended through the entire region, became one of the most considerable of Greece. He made a number of journeys outside Greece and was present when the Apostles were assembled at the Dormition and glorious Assumption of the Mother of God. He wrote of Her, and he became a friend of Saint John, Her guardian. He corresponded with Saint Timothy, Saint Titus, Saint Polycarp and others of the Apostles’ successors. It appears that it was after a conversation with Saint John the Apostle that Saint Denys, already in his late sixties, determined to go to the Occident to preach to the idolaters of that region. He left Saint Publius as his successor in Athens, and departed for Rome with Eleutherius and Rusticus. Pope Saint Clement of Rome confirmed this enterprise, and added to the group at least ten more priests, all of whom are now listed among the Saints. The authors of the oriental church are steadfast in asserting, with Roman tradition, that it was Saint Denys the Areopagite, converted by Saint Paul, who was sent to Gaul. Others have thought Saint Denys was a fourth century missionary, but this theory cannot be credited, as the Bollandists explain at length. (Vol. 14)
Through him and his disciples, whom he sent to evangelize various districts, the sees of Rouen, Chartres, Evreux, Verdun, and Beauvais were established. With his two original companions, Eleutherius and Rusticus, Saint Denis went to Paris, where he built four oratories. The first baptized Christian, who received them into his house, was decapitated, denounced to a Roman official by his own pagan wife, as an accomplice of their three guests. The three missionaries were imprisoned and chained in such a way as to suffer torture, then flogged while they blessed God. Other torments were devised, but God preserved the bishop, at this time nearly 100 years old. They were finally beheaded on Montmartre; a large group of Christians, who wept on this occasion, as well as others of the city and the entire region, were also massacred. The wife of the first Parisian Christian and martyr was converted and died with the others. Their joint martyrdom occurred about the year 117.
Les Petits Bollandistes: Vies des Saints, by Msgr. Paul Guérin (Bloud et Barral: Paris, 1882), Vol. 12