John Barham Day (1793–1860) was a British Jockey and Trainer. For much of his career he was usually known simply as John Day: when his son of the same name rose to prominence, the older man was referred to as John Barham Day, John Day, Sr. or Old John Day. A member of a highly successful racing family, Day first made his name as a jockey in the 1820s and rode the winners of sixteen classics before retiring. In the mid-1830s he set up as a trainer of racehorses at Danebury near Stockbridge.