St. Denis of Paris was a bishop and martyr. It is reported that Denis was born in Italy and then sent into Gaul (modern France) with five or six other bishops. He then became the first bishop of Lutetia (modern Paris).

Denis was arrested with Rusticus, a priest, and Eleutherius, a deacon. Denis was martyred for his faith by decapitation on Montmarte hill. This was during the last days of the persecution of the Church under Emperor Trajanus Decius (r. 249-251).

After having his head cut off, Denis is said to have walked for several miles while holding it and delivering a sermon on repentance.

A chapel was raised at the site of his burial by a local Christian woman, Genevieve; it was later expanded into an abbey and basilica, which because the burial place of the kings of France. Around this grew the city of Saint-Denis, now a suburb of Paris.

Denis is also one of the Fourteen Holy Helpers who are a group of saints venerated together in Catholic tradition because their intercession is believed to be particularly effective against specific diseases and dangers. Each saint is invoked for aid regarding particular ailments or needs. The Fourteen Holy Helpers are: Acacius, Barbara, Blaise, Catherine of Alexandria, Christopher, Cyriacus, Denis, Erasmus of Formia, Eustace, George, Giles, Margaret of Antioch, Pantaleon, and Vitus.