Thomas Tanner (24 January 1674 – 14 December 1735) was an English antiquary and prelate.
He was born at Market Lavington in Wiltshire, and was educated at The Queen's College, Oxford, taking holy orders in 1694. The following year, he became chaplain and then fellow of All Souls', and a few years later private chaplain to John Moore, bishop of Norwich, and afterwards bishop of Ely, who appointed him chancellor of the diocese of Norwich. He lived in Norfolk from 1701 until 1731. In 1706 he became rector of Thorpe, near Norwich, and in 1713 a canon of Ely Cathedral, in 1724 a canon of Christ Church, Oxford. On 23 January 1732 he was appointed Bishop of St Asaph and thereafter divided his time between London, Oxford and North Wales. He died in Oxford.
Tanner's chief work published during his lifetime is the Notitia Monastica, a short account of all the religious houses in England and Wales. This was published at Oxford in 1695; it was reprinted with additions by the author's brother, John Tanner, in 1744; and was reprinted again with further additions by James Nasmith in 1787. He also wrote Bibliotheca Britannico-Hibernica, a dictionary of all the authors who flourished in England, Scotland and Ireland before the opening of the 17th century, at which he laboured for forty years. This was eventually completed by David Wilkins and published in 1748, thirteen years after the author's death. Tanner also collected materials for a history of Wiltshire and worked for some time on a new edition of the works of John Leland. His valuable collection of books and manuscripts is in the Bodleian Library at Oxford.