REGULUS or RULE, Saint (fl. 8th cent.?), was the legendary founder of the see of St. Andrews. He is a leading character in the story of the journeyings of the relics of St. Andrew, a story which has three principal versions—that of a Colbertine manuscript (the oldest and simplest of the three), that of St. Andrews priory, and that of the Aberdeen breviary. These versions vary considerably in detail, but the main outline of the story is that when in 345 Constantius invaded Patras, where St. Andrew was martyred, Bishop Regulus, custodian of the relics, concealed a part of them in obedience to a vision; he was directed in a second vision to found a church in the west. After some wandering, Regulus reached Scotland, and on a hill called Rigmond (Kil-rymont, or St. Andrews) met the king of the Picts at the head of an army. The king was Ungus, son of Urguist, who had already been warned in a vision to offer the tenth part of his inheritance to St. Andrew in order that he might be victorious in the war he was waging against the Britannic nations in the plain of Merse, or, according to the St. Andrews version, against Æthelstan, king of the Saxons. The relics of St. Andrew were landed at a harbour called Matha—that is, Mordurus or Muckross. The king then dedicated that place to St. Andrew, to be head of all the Pictish churches, and made a grant of Kilrymont and a large territory to God and St. Andrew, together with the sites of many other churches which the legend specifies.
Skene identifies Ungus or Hungus, son of Urguist, the benefactor of Regulus, with Angus McFergus, who reigned 731–761, and led in 740 an expedition against Eadbert, king of Northumbria. The ‘Register of St. Andrews,’ however, attributed the foundation of St. Andrews to a later Angus McFergus, who reigned 822–834. It is impossible to reconcile the dates of either Angus with those assigned in legend to Regulus, who is said to have left Patras for Scotland in the fourth century. But no reliance can be placed on that part of the story; there is doubtless some confusion between the founder of the Scottish see of St. Andrews and another St. Regulus or Rieul, a Greek of the fourth century, who was first bishop of Senlis.
The cult of St. Andrew in the eighth century in Scotland was perhaps due to the wanderings of Acca [q. v.]; the latter had ruled over Hexham, which was dedicated to St. Andrew, and the church there claimed to possess his relics. St. Regulus is commemorated in the Aberdeen breviary on 30 March. When 30 March fell in Lent, St. Regulus's feast was commemorated on 17 Oct. On the preceding day the feast of an Irish saint, Riaghail, is celebrated, and it has been suggested that this name is the Celtic form of the Latin Regulus. In Scotland St. Regulus is patron of churches at Monifeth, Kennethmont, Meikle Folla, and Ecclesgreg.[Forbes's Cal. of Scottish Saints, p. 436; Brev. Aberd. Prop. SS. pars hyem. f. lxxxii, edited for the Bannatyne Club; Skene's Celtic Scotland, and paper in the Proceedings of the Society of Antiquaries of Scotland, iv. 300–21; Reeves's Culdees, pt. iii. § 2; Acta SS. Bolland. Oct. viii. 163; Dict. of Christian Biogr.; O'Hanlon's Irish Saints, iii. 1021.]