John Calcraft the elder (1726 – 23 August 1772), of Rempstone in Dorset and Ingress in Kent, was an English army agent and politician.
The son of an attorney who was Town Clerk of Grantham, Calcraft set out on a career as an army contractor under the patronage of Grantham's Member of Parliament (MP), the Marquess of Granby, at this period a rising army officer, and of one of the Whig leaders in Parliament, Henry Fox, to whom he was apparently related. (The nature of the relationship was never made clear, and insinuations were made that he was Fox's natural son.) Calcraft was deputy paymaster of the Duke of Cumberland's army at the time of the Jacobite Rebellion, and subsequently a clerk in the War Office (1747–56), paymaster of widow's pensions (1757–62) and deputy-commissary of musters (1756–63). All of these posts offered lucrative opportunities for enrichment, both legitimate and less so. As well as the functions directly arising from the offices he held, he was involved with the rebuilding of Horse Guards, held contracts for delivering coal to Gibraltar, and became agent to many regiments of the army, a role with both administrative and financial responsibilities and offering considerable opportunity for profit if ably handled. By 1761, he was acting for no less than 49 colonels. Calcraft amassed a considerable fortune.
In 1757 Calcraft purchased an estate at Rempstone on the Isle of Purbeck in Dorset, which gave him an interest in three nearby parliamentary boroughs, Corfe Castle, Poole and Wareham. He quickly set out to buy further property which would increase his influence in each borough: he was unsuccessful at Corfe Castle, but acquired sufficient sway at Poole to secure the election of his brother, Thomas Calcraft, in 1761 and 1768, and became landlord to enough of the voters to gain complete control of Wareham, which remained a Calcraft pocket borough until the Reform Act. In 1760 he bought a further estate, at Ingress near Dartford in Kent.