- WILLIAMS, WILLIAM HUGH (Arafon; 1848 - 1917), trade union leader
- WILLIAMS, WILLIAM JOHN (1878 - 1952), H.M. Inspector of Schools and Director of the Council of Social Service for Wales and Monmouthshire
- WILLIAMS, WILLIAM JONES (1863 - 1949), civil servant, secretary of Kodak Limited, treasurer of Coleg Harlech and Urdd Gobaith Cymru
- WILLIAMS, WILLIAM JONES (1891 - 1945), revivalist, Apostolic pastor
- WILLIAMS, WILLIAM LLEWELYN (1867 - 1922), Member of Parliament, lawyer, and author
- WILLIAMS, WILLIAM MATTHEWS (1885 - 1972), musician
- WILLIAMS, WILLIAM MORRIS (1883 - 1954), quarryman, choir conductor, soloist and cerdd dant adjudicator
- WILLIAMS, WILLIAM NANTLAIS (1874 - 1959), minister (Presb.), editor, poet and hymn writer
- WILLIAMS, WILLIAM OGWEN (1924 - 1969), archivist, university professor
- WILLIAMS, WILLIAM PRICHARD (1848 - 1916), co-founder of the Princes Road Presbyterian church, Bangor, and publisher of a new edition of Deffynniad Ffydd Eglwys Loegr by Maurice Kyffin
- WILLIAMS, WILLIAM RETLAW JEFFERSON (c.1863 - 1944), solicitor, genealogist, and historian
- WILLIAMS, WILLIAM RICHARD (1896 - 1962), minister (Presb.) and Principal of the United Theological College, Aberystwyth
- WILLIAMS, Sir WILLIAM RICHARD (1879 - 1961), railway traffic inspector
- WILLIAMS, WILLIAM SIDNEY GWYNN (1896 - 1978), musician and administrator
- WILLIAMS, WILLIAM WYN (1876 - 1936), minister and poet
- WILLIAMS, ZACHARIAH (1673 - 1755), medical practitioner, and inventor
- WILLIAMS, ZEPHANIAH (1795 - 1874), Chartist
- WILLIAMS-ELLIS, JOHN CLOUGH (1833 - 1913), scholar, clergyman, poet and possibly the first Welshman to climb one of the highest mountains in the Alps
- WILLIAMS-WYNN, Sir ROBERT WILLIAM HERBERT WATKIN (1862 - 1951) - see WYNN
- WILLIAMSON, EDWARD WILLIAM (1892 - 1953), Bishop of Swansea and Brecon
- WILLIAMSON, OWEN (1840 - 1910), schoolmaster - see WILLIAMSON, ROBERT MONA
- WILLIAMSON, ROBERT (MONA) (Bardd Du Môn; 1807 - 1852), teacher and poet
- WILLIS, ALBERT CHARLES (1876 - 1954), president of the Australian Labour Party
- WILLIS, BROWNE (1682 - 1760), antiquary - see WOTTON, WILLIAM
- WILLIS, JOHN WILLIAM - see WILLIS-BUND, JOHN WILLIAM
- WILLIS-BUND, JOHN WILLIAM (1843 - 1928), writer on the history of the Welsh Church
- WILSON, Bwlch-y-llyn - see WILSON, RICHARD
- WILSON, AARON (1586 - 1643), cleric - see WILSON, JOHN
- WILSON, HERBERT REES (1929 - 2008), scientist
- WILSON, JOHN (1626 - c.1695/6), playwright
- WILSON, RICHARD (1713 - 1782), landscape painter
- WINFIELD, HERBERT BENJAMIN (1879 - 1919), Wales and Cardiff Rugby full-back
- WINIFRED - see GWENFREWI
- WINSTONE, JAMES (1863 - 1921) South Wales, miners' leader
- WINTER, CHARLES (1700 - 1773), Arminian Baptist minister
- WIRRIOTT, - see OWEN
- WMFFRE DAFYDD ab IFAN - see DAVIES, HUMFFREY
- WOGAN family
- WOOD family, Welsh gipsies
- WOOD, JEREMIAH (1778? - 1867), harpist - see WOOD
- WOOD, MARY MYFANWY (1882 - 1967), missionary in China, 1908-51
- WOOD, RONALD KARSLAKE STARR (1919 - 2017), botanist
- WOOD, THOMAS (1777 - 1860), Member of Parliament - see WILLIAMS
- WOODING, DAVID LEWIS (1828 - 1891), genealogist, historian, bibliophile and shopkeeper
- WOOLLER, WILFRED (1912 - 1997), cricketer and rugby player
- WORCESTER, Marquesses of - see SOMERSET
- WORTHINGTON, WILLIAM (1704 - 1778), cleric and author
- WOTTON, WILLIAM (1666 - 1727), cleric and scholar
- WROTH, WILLIAM (1576 - 1641), Puritan cleric, and founder of the first Independent church in Wales
- WYN, OWEN, master of S. John's College, Cambridge - see WYNN