John Horsley (c. 1685 – 12 January 1732) was a British antiquarian, known primarily for his book Britannia Romana or The Roman Antiquities of Britain which was published in 1732.
John Hodgson, in a memoir published in 1831, held that Horsley was born in 1685, at Pinkie House, in the parish of Inveresk, Midlothian, and that his father was a Northumberland nonconformist, who had migrated to Scotland, but returned to England soon after the Glorious Revolution of 1688. John Hodgson Hinde, in the Archaeologia Aeliana of February 1865, held that he was a native of Newcastle-on-Tyne, the son of Charles Horsley, a member of the Tailors' Company of the town. David Boyd Haycock writing in the Oxford Dictionary of National Biography comments that none of the suggestions made for Horsley's background is verifiable.
He was educated at the Royal Grammar School, Newcastle and at Edinburgh University, where he graduated MA on 29 April 1701. There is evidence that he "was settled in Morpeth as a Presbyterian minister as early as 1709." Hodgson, however, thought that up to 1721, at which time he was residing at Widdrington, "he had not received ordination, but preached as a licentiate."
Horsley communicated to the Philosophical Transactions notes on the rainfall at Widdrington in the years 1722 and 1723. At Morpeth Horsley opened a private school, attracting pupils irrespective of religious connection, among them Newton Ogle, later dean of Westminster. He gave lectures on mechanics and hydrostatics in Morpeth, Alnwick and Newcastle, and was elected a Fellow of the Royal Society on 23 April 1730, or in May, 1729.