- THOMAS, RICHARD (1753 - 1780), cleric, transcriber and collector of manuscripts, and genealogist
- THOMAS, RICHARD (1718 - 1807), Methodist exhorter
- THOMAS, RICHARD (1838 - 1916), industrialist
- THOMAS, RICHARD (1871 - 1950), minister (CM) and writer
- THOMAS, ROBERT (d. 2 April 1692), Puritan preacher
- THOMAS, ROBERT (Ap Vychan; 1809 - 1880), Independent minister and tutor, poet and man of letters
- THOMAS, ROBERT (1796 - 1866), Calvinistic Methodist preacher, a 'character'
- THOMAS, ROBERT (d. 1774), poet, and sexton of Llanfair Talhaearn Denbighshire
- THOMAS, ROBERT (1782 - 1860), printer and publisher
- THOMAS, ROBERT DAVID (Iorthryn Gwynedd; 1817 - 1888), Independent minister
- THOMAS, ROBERT JERMAIN (1840 - 1866), missionary pioneer of the London Missionary Society
- THOMAS, Sir ROBERT JOHN (1873 - 1951), politician and shipowner
- THOMAS, Sir ROGER (1886 - 1960), pioneer of modern agriculture
- THOMAS, RONALD STUART (1913 - 2000), poet and clergyman
- THOMAS, ROWLAND (c. 1887 - 1959), newspaper proprietor
- THOMAS, SAMPSON (1739 - 1807), early Calvinistic Methodist exhorters
- THOMAS, SAMUEL (1692 - 1766), Independent minister, and tutor of Carmarthen Academy
- THOMAS, SAMUEL (1800 - 1879), coal prospector - see THOMAS, DAVID ALFRED
- THOMAS, SIDNEY GILCHRIST (1850 - 1885), metallurgist and inventor
- THOMAS, SIENCYN (1690 - 1762), boot-maker, Dissenting preacher, and poet
- THOMAS, SIMON (d. 1743?), Presbyterian minister and author
- THOMAS, STAFFORD HENRY MORGAN (1896 - 1968), minister (Presb.) and poet
- THOMAS, THOMAS (1880 - 1911), first British middle-weight boxing champion
- THOMAS, THOMAS (1776 - 1847), cleric and historian
- THOMAS, THOMAS (1804 - 1877), cleric
- THOMAS, THOMAS (1805 - 1881), Baptist minister and college principal
- THOMAS, THOMAS (1839 - 1888), Wesleyan minister, and miscellaneous writer
- THOMAS, THOMAS (1759 - 1819), Baptist minister - see THOMAS, TIMOTHY (I)
- THOMAS, THOMAS ap (1829 - 1913), musician - see THOMAS, JOHN
- THOMAS, THOMAS EMLYN (Taliesin Craig-y-felin; 1822 - 1846), Unitarian minister, poet, and schoolmaster
- THOMAS, THOMAS GEORGE (Viscount Tonypandy), (1909 - 1997), Labour politician and Speaker of the House of Commons
- THOMAS, THOMAS HENRY (Arlunydd Penygarn; 1839 - 1915), artist
- THOMAS, THOMAS JACOB (Sarnicol; 1873 - 1945), schoolmaster, writer and poet
- THOMAS, THOMAS LLEWELYN (1840 - 1897), vice-principal Jesus College - see THOMAS, THOMAS
- THOMAS, THOMAS LLEWELYN (1840 - 1897), scholar, teacher and linguist
- THOMAS, THOMAS MORGAN (1828 - 1884), missionary
- THOMAS, TIMOTHY (1694 - 1751), cleric and scholar
- THOMAS, TIMOTHY (1754 - 1840), Baptist minister - see THOMAS, Timothy I
- THOMAS, TIMOTHY (1753 - 1827), Baptist minister - see THOMAS, JOSHUA
- THOMAS, TIMOTHY (1720 - 1768) Maes-isaf, Pencarreg, Baptist minister and author
- THOMAS, WILLIAM (Islwyn; 1832 - 1878), Calvinistic Methodist minister, and poet
- THOMAS, WILLIAM (Glanffrwd; 1843 - 1890), cleric and author
- THOMAS, WILLIAM (Gwilym Marles; 1834 - 1879), Unitarian minister, social reformer, writer, and schoolmaster
- THOMAS, WILLIAM (d. 1813), Unitarian Baptist minister
- THOMAS, WILLIAM (Gwilym Mai; 1807 - 1872), poet and printer
- THOMAS, WILLIAM (1832 - 1911), Congregational minister
- THOMAS, WILLIAM (d. 1554), Italian scholar and clerk of the Privy Council to king Edward VI
- THOMAS, WILLIAM (1749 - 1809), Independent minister, and publisher
- THOMAS, WILLIAM (fl. c . 1685? - c . 1740?), secretary to Robert Harley, 1st earl of Oxford
- THOMAS, WILLIAM (d. 1671), leader of the free-communion Baptists in the South of that county in Restoration times