- WILLIAMS, THOMAS (fl. end of the 18th century), attorney, outstanding figure in the copper industry
- WILLIAMS, THOMAS (1658 - 1726), cleric and translator
- WILLIAMS, THOMAS (Brynfab; 1848 - 1927), littérateur and farmer
- WILLIAMS, THOMAS (Tom Nefyn; 1895 - 1958), minister (Presb.) and evangelist
- WILLIAMS, THOMAS (Capelulo; c.1782 - 1855), reformed drunkard, itinerant bookseller, 'character'
- WILLIAMS, THOMAS (1755 - 1839), bookseller - see WILLIAMS, EVAN
- WILLIAMS, THOMAS CHARLES (1868 - 1927), Calvinistic Methodist minister
- WILLIAMS, Sir THOMAS HERBERT PARRY- - see PARRY-WILLIAMS, Sir THOMAS HERBERT
- WILLIAMS, THOMAS HUDSON - see HUDSON-WILLIAMS, THOMAS
- WILLIAMS, THOMAS LLOYD (1830 - 1910), Welsh-American writer
- WILLIAMS, Sir THOMAS MARCHANT (1845 - 1914), barrister and writer
- WILLIAMS, THOMAS OSWALD (ap Gwarnant; 1888 - 1965), Unitarian minister, author, poet and public figure
- WILLIAMS, THOMAS RHONDDA (1860 - 1945), Congregational minister
- WILLIAMS, TOM PUGH (1912 - 1985), university professor
- WILLIAMS, Sir TREVOR (c. 1623 - 1692) Llangibby, politician
- WILLIAMS, VICTOR ERLE NASH - see NASH-WILLIAMS, VICTOR ERLE
- WILLIAMS, WALDO GORONWY (1904 - 1971), poet and pacifist
- WILLIAMS, WATKIN HEZEKIAH (Watcyn Wyn; 1844 - 1905), schoolmaster, poet, and preacher
- WILLIAMS, WILLIAM (1781 - 1840), Independent minister
- WILLIAMS, WILLIAM (1788 - 1865), Member of Parliament
- WILLIAMS, WILLIAM (Gwilym Cyfeiliog; 1801 - 1876), poet and hymn-writer
- WILLIAMS, WILLIAM (Gwilym Peris; 1769 - 1847), poet
- WILLIAMS, WILLIAM (Carw Coch; 1808 - 1872), eisteddfodwr and man of letters
- WILLIAMS, WILLIAM (1748 - 1820), cleric, a pioneer of the Sunday school movement in Wales
- WILLIAMS, WILLIAM (Gwilym Twrog; 1768 - 1836), poet
- WILLIAMS, WILLIAM (1747 - 1812), Evangelical cleric
- WILLIAMS, WILLIAM (Gwilym ab Ioan; 1800 - 1868), Welsh-American poet
- WILLIAMS, WILLIAM (1732 - 1799), Baptist minister, and justice of the peace
- WILLIAMS, WILLIAM (1717 - 1791), Methodist cleric, author, and hymn-writer
- WILLIAMS, WILLIAM (1738 - 1817) Llandygái, antiquary, author, prominent official at Cae-braich-y-cafn quarry
- WILLIAMS, Sir WILLIAM (1634 - 1700), lawyer and politician
- WILLIAMS, WILLIAM (c. 1625 - 1684), antiquary
- WILLIAMS, WILLIAM (fl. 1648-1677), author of Poetical Piety
- WILLIAMS, WILLIAM (Caledfryn; 1801 - 1869), Congregational minister, poet, and critic
- WILLIAMS, WILLIAM (Myfyr Wyn; 1849 - 1900), blacksmith, poet and local historian
- WILLIAMS, WILLIAM (1817 - 1900), Calvinistic Methodist minister, and author
- WILLIAMS, WILLIAM (Ap Caledfryn; 1837 - 1915), portrait painter
- WILLIAMS, WILLIAM (Gwilym ab Iorwerth; 1800? - 1859), poet
- WILLIAMS, WILLIAM (1832 - 1900), veterinary surgeon
- WILLIAMS, WILLIAM (fl. 1853), translator and author
- WILLIAMS, WILLIAM (Creuddynfab; 1814 - 1869), poet and literary critic
- WILLIAMS, WILLIAM (Crwys; 1875 - 1968), poet, preacher, archdruid
- WILLIAMS, WILLIAM (1717 - 1800), Independent minister - see WILLIAMS, ABRAHAM
- WILLIAMS, Sir WILLIAM (d. 1740), baronet - see WILLIAMS, Sir WILLIAM
- WILLIAMS, WILLIAM - see WILLIAMS, Roger
- WILLIAMS, WILLIAM ALBERT (1909 - 1946), organist, music critic and composer
- WILLIAMS, WILLIAM AUBREY (Gwilym Gwent; 1834 - 1891), musician
- WILLIAMS, WILLIAM EMYR (1889 - 1958), solicitor and eisteddfod patron
- WILLIAMS, WILLIAM EWART (1894 - 1966), physicist and inventor
- WILLIAMS, WILLIAM GILBERT (1874 - 1966), schoolmaster and local historian