Sir William Williams (1634-1700) was a lawyer, MP for Chester and later for Beaumaris, and the first Welshman to become Speaker of the House of Commons, a post which he held from 1680 to 1685. A critic of King James II, he was nevertheless appointed Solicitor-General after a dispute with fellow Welshman Judge Jeffreys. He helped to draft the Declaration of Rights. Williams was knighted in 1687 and created a baronet in 1688.
William Williams Pantycelyn (1717-1791) was a religious leader and hymnwriter.
William Williams (8 April 1731 - 2 August 1811) was an American patriot and a signer of the Declaration of Independence.
William Williams of Wern (1781-1840) was an Independent minister, the promoter of the "General Union" movement of 1834. He was one of three "giants of the Welsh pulpit", along with John Elias and Christmas Evans.
William Williams (1788-1865) was a Welsh businessman based in London. As Radical MP for Coventry (1835-1847) and Lambeth (1850-1865), he was critical of the state of Welsh education and instigated the Commission which made its controversial report in 1847 (the Treason of the Blue Books). His own bequest was used to promote university education in Wales.
Sir William Fenwick Williams (1800-1883) was a Canadian-born British military leader.
William Williams (1808-1872), known as "Red Stag" (in Welsh, "Carw Coch") was proprietor of the Stag Inn at Trecynon, from which he derived his nickname. He was a local politician, one of the society of "Free Enquirers" at Aberdare, subsequently known as the "Cymreigyddion of Carw Coch".
William Williams (1832-1900) was a Welsh veterinary surgeon, founder of the New Veterinary College in Edinburgh (1871) and author of several standard works on veterinary science.
William Williams (bardic name, "Crwys") (1875-1968) was a Welsh language poet, three times winner of the Crown at the National Eisteddfod of Wales and later Archdruid (1939-1947). His best-known works include "Ednyfed Fychan" (1910) and "Dysgub y Dail".
William Carlos Williams was an American poet.