John Leng (1665–1727) was an English churchman and academic, bishop of Norwich from 1723.
He was born at Thornton le Dale, near Pickering, in Yorkshire. He received his early education at St. Paul's School, and obtained an exhibition at Catharine Hall, Cambridge, where he was admitted as a sizar 26 March 1683. He graduated B.A. in 1686. His subsequent degrees were M.A. 1690, B.D. 1698, D.D. 1716.
He was elected fellow of his college 13 September 1688, and subsequently became known as a tutor and Latinist. scholar. At the consecration of the new chapel of his college by Simon Patrick, bishop of Ely, in 1701, he preached the sermon. In 1708 he was presented by his old pupil, Sir Nicholas Carew, to the rectory of Beddington, Surrey, which he held in commendam to his death.
In 1717 and 1718 he delivered the Boyle Lectures, which were published the following year, his subject being The Natural Obligations to believe the Principles of Religion and Divine Revelation. He became chaplain in ordinary to George I, and in 1723 was appointed bishop of Norwich. He was consecrated at Lambeth by Archbishop William Wake on 3 November of the same year.