John de Haydock (c.1322 – December 12, 1387) was the 22nd great-grandfather of Cometan, classified as one of Cometan’s medieval paternal ancestors in the Taylor family line.

Born in Haydock, Warrington, Lancashire, John was the husband of Joanna de Dutton and is also known to have been the father of Sir Gilbert de Haydock IV. John is recorded as having been the son of Gilbert de Haydock III and Emma de Haydock.

In Cometanic ancestry, John de Haydock is categorised as part of the 24th generation retrograde, and because he was born before 1453, he is classified as a medieval ancestor of Cometan, a title that is rarely bestowed.