Regulus, also recorded under the forms Reol and Rieul, was a seventh-century monk and hierarch of Gaul who is venerated among the pre-schism Western saints of the Orthodox Church. By tradition he began his monastic life at the abbey of Rebais in France, where he was a companion and disciple of Saint Philibert, the monastic founder later associated with Jumieges and Noirmoutier. He is commemorated on September 3.
From the monastic community at Rebais, Regulus was raised to the see of Reims, becoming archbishop of that ancient and prominent church. He is reckoned among the bishops of Reims in succession to Saint Nivard, who had held the see before him. As archbishop he is chiefly remembered for founding the monastery of Orbais, in the valley of the Surmelin, which became a Benedictine house following the Rule of Saint Benedict and was settled in part by monks drawn from his own former monastery of Rebais.
Regulus is distinguished in the tradition from the several other saints who bear the name Regulus, and in particular from Regulus of Tuscany, who is commemorated on September 1. He reposed in 698 and, according to later record, was buried at the abbey church of Saint-Pierre at Orbais, which he had founded.