William Blenkiron (1807?–1871) was an English breeder of racehorses.
Blenkiron was born in Marrick, Richmond, Yorkshire, about 1807. He was originally brought up as a farmer, but he abandoned that pursuit, and moved to London in 1834, and began business as a general agent in Cheapside. In 1845, he added to his establishment a manufactory of stocks and collars, and three years later retired in favour of his son.
Blenkiron always desired to be the owner of a racehorse, and in 1847, while residing at Dalston, he purchased a mare named Glance. She was by Venison out of Eyebrow, by Whisker, one of Lord George Bentinck's breeding. In course of time she bore a colt, Young Beverlac, which ran at race meetings with moderate success. The colt was afterwards exchanged for three mares, and these formed the commencement of a stud destined to become the most celebrated of any establishment of horses in Europe.
About 1852, Blenkiron, wanting more room, moved from Dalston to Middle Park, Kent. He brought with him seven or eight brood mares, and Neasham, the head of the list of Eltham sires. The establishment now rapidly increased, until it was augmented to upwards of two hundred of the highest class and best mares that money and experience could produce. Kingston, Touchstone, Birdcatcher, and Newminster were the four cornerstones of his extensive stud, and it was to the first of these that he, to a great extent, owed his success as a breeder; for that horse was the sire of Caractacus, who was perhaps the most sensational Derby winner on record.