Thomas Rees (13 December 1815 - 29 April 1885) was a Welsh Congregational minister and historian of nonconformism.
The son of Thomas Rees and his wife Hannah William, Rees was born at Pen Pontbren, Llanfynydd, Carmarthenshire, and brought up by his mother's family at Banc-y-fer, Llangathen, where he helped his grandfather, Dafydd William, a basket maker. He joined the Independent chapel at Capel Isaac and began to preach in March 1832. He took a job at a colliery at Llwydcoed, Aberdare, but fell ill and then set up a small school. In 1836 he moved to Craig-y-bargod, Merthyr Tudful, and took charge of a small school there.
Rees was ordained a minister on 15 September 1836 and thereafter served at pastorates at Craig-y-Bargoed (1836), Trecynon, Aberdare (1840), Llanelli (1842), Cendl (Beaufort), Breconshire/Mon. (1849) and Abertawe (1860). His chapel in Beaufort was Carmel Chapel and Beaufort was in the county of Brecknockshire (Breconshire) until 1879: see photos of Carmel Chapel on the Beaufort website. He was awarded an honorary doctorate of divinity in 1862 by Marietta College, Ohio. He was twice elected chairman of the Union of Welsh Independents (in 1873 and 1875), and elected chairman of the Congregational Union of England and Wales in 1884, but died before his term of office was to begin.
Rees was widely known for his biblical commentaries. He was a co-founder of the first Welsh Independent quarterly, Yr Adolygydd. His History of Protestant Nonconformity in Wales (1861, 2nd e. 1883) prepared the ground for a history of Welsh Independent churches, Hanes eglwysi Annibynol Cymru (1870 onwards), on the first four volumes of which he worked with John Thomas (1821–1892). He was criticized for denominational prejudice in the work, but made meticulous use of sources, so that it remains an important source work.