Regulus (1739) was an undefeated British Thoroughbred racehorse who won eight Royal Plates in 1745.

Regulus was by the Godolphin Arabian, his dam, the noted Grey Robinson, by Bald Galloway and out of Sister To Old Country Wench (dam of Squirt ) by Snake, out of Old Grey Wilkes, a daughter of Old Hautboy.

[2] Regulus was superior to any horse of his time and retired unbeaten to stud in the north of England.

At stud, he sired Royal (1749), South (1750), Fearnought (1755), undefeated Alipes, Star, Cato, Juba, Ascha, Grisewood's Lady Thigh, Miss Belsea, and many successful broodmares including Spilletta who is the dam of the undefeated champion Eclipse.

[2] His offspring's successes led him to be the Leading sire in Great Britain & Ireland for eight years (1754–1757, 1761, 1763, 1765, and 1766).