John Vernon (c. 1618 – 13 March 1670) was Quartermaster-General of Oliver Cromwell’s army and third son of Sir Edward Vernon, of Houndshill, Staffordshire, England. John obtained title to Clontarf Castle near Dublin in 1649 through a financial arrangement with John Blackwall who had been granted the estate by Oliver Cromwell. Thereafter the Vernons occupied the castle for approximately 300 years.