Samuel Horsley (September 15, 1733 - October 4, 1806), English divine, was born in London.

Entering Trinity College, Cambridge, he became LL.B. in 1758 without graduating in arts, and in the following year succeeded his father in the living of Newington Butts in Surrey. Horsley was elected a Fellow of the Royal Society in 1767; and secretary in 1773, but, in consequence of a difference with the president (Sir Joseph Banks) he withdrew in 1784. In 1768 he attended the eldest son of the 4th earl of Aylesford to Oxford as private tutor; and, after receiving through the earl and Bishop Lowth various minor preferments, which by dispensations he combined with his first living, he was installed in 1781 as archdeacon of St Albans.

Horsley now entered in earnest upon his famous controversy with Joseph Priestley, who denied that the early Christians held the doctrine of the Trinity. In this controversy, conducted on both sides in the fiercest polemical spirit, Horsley showed the superior learning and ability. His aim was to lessen the influence which the prestige of Priestley's name gave to his views, by indicating inaccuracies in his scholarship and undue haste in his conclusions. For the energy displayed in the contest Horsley was rewarded by Lord Chancellor Thurlow with a prebendal stall at Gloucester; and in 1788 the same patron procured his promotion to the see of St David's.

As a bishop, Horsley was energetic both in his diocese, where he strove to better the position of his clergy, and in parliament. The efficient support which he afforded the government was acknowledged by his successive translations to Rochester in 1793, and to St Asaph in 1802. With the bishopric of Rochester he held the deanery of Westminster. He died at Brighton on the 4th of October 1806.

Besides the controversial Tracts, which appeared in 1783-1785, 1786, and were republished in 1789 and 1812, Horsley's more important works are:

• Apollonii Pergaei inclinationum libri duo (1770)
• Remarks on the Observations ... for determining the acceleration of the Pendulum in Lat. 7o 51' (1774)
• Isaaci Newtoni Opera quae extant Omnia, with a commentary (5 vols 4to, 1779-1785)
• On the Prosodies of tke Greek and Latin Languages (1796)
• Disquisitions on Isaiah xviii. (1796)
• Hosea, translated ... with Notes (1801)
• Elementary Treatises on ... Mathematics (1801)
• Euclidis elernentorum libri priores XII. (1802)
• Euclidis datorum liber (1803)
• Virgil's Two Seasons of Honey, &c. (1805)
• papers in the Philosophical Transactions from 1767 to 1776

After his death there appeared:

• Sermons (1810-1812)
• Speeches in Parliament (1813)
• Book of Psalms, translated with Notes (1815)
• Biblical Criticism (1820)
• Collected Theological Works (6 vols 8vo, 1845).