John Topham (1746–1803) was an English official, librarian and antiquary.
Born on 6 January 1746 at Elmly near Huddersfield, he was the third son of Matthew Topham (died 1773), vicar of Withernwick and Mappleton in Yorkshire, and of his wife Ann, daughter of Henry Willcock of Thornton in Craven. John Topham went to London while still young with a minor appointment under Philip Carteret Webb, solicitor to the Treasury. By influence he obtained a place in the State Paper office with Sir Joseph Ayloffe and Thomas Astle.
On 5 February 1771 Topham was admitted to Lincoln's Inn, and on 5 April 1779 he was elected a Fellow of the Royal Society. In May 1781 he was appointed a deputy-keeper of the state papers, and in April 1783 a commissioner in bankruptcy. On 19 March 1787 he became a bencher of Gray's Inn, and on 29 Nov. was elected treasurer of the Society of Antiquaries of London, to which he had been admitted a Fellow in 1767. About 1790 he became librarian to the Archbishop of Canterbury, in succession to Michael Lort. He also filled the offices of registrar to the charity for the relief of poor widows and children of clergymen and of treasurer to the orphan charity school.
Topham died without issue at Cheltenham on 19 August 1803, and was buried in Gloucester Cathedral, where a marble monument was erected to him in the nave. On 20 August 1794 he has married Mary, daughter and coheiress of Mr. Swinden of Greenwich, Kent.