Sir William Humfreys, 1st Baronet (also spelled Humphreys; died 26 October 1735), was a British ironmonger and politician.
He was the only son of ironmonger Nathaniel Humfreys of Candlewick Street, London. His father was the second son of William Ap Humfrey, of Penrhyn, Montgomeryshire. He followed his father into the ironmongery trade of London, and was Master of the Worshipful Company of Ironmongers in 1705. He became an oilman and drysalter in Poultry, London, living afterwards in Bloomsbury Square.
He was Sheriff of London, 1704–05, and was knighted on 26 October 1704. He was Alderman of Cheap Ward from 29 July 1707, and of Bridge Without from 25 January 1733 until his death. He was Member of Parliament in the Parliament of Great Britain for Marlborough from 1715 to 1722.
He was Lord Mayor of London for 1714–15, and in that capacity officiated on 20 October 1714 at the Coronation of the British monarch, George I of Great Britain, entertaining the King and his court at Guildhall, London. He was created a baronet in the baronetage of Great Britain on 30 November 1714.
He was President of Bridewell and Bethlehem Hospitals, Lord of the Manors of Barking and Dagenham, and lived at Hever Castle in Kent.
He married firstly Margaret Wintour, daughter of William Wintour of Dymock, Gloucestershire. She died on 19 August 1704, and was buried at St Mildred, Poultry. He married secondly, on 6 January 1705 at Knightsbridge Chapel, Ellen, the widow of Col. Robert Lancashire of London. He had no issue by his second wife, and she died on 25 March 1732. He died on 26 October 1735, and was buried on 6 November 1735 at St Mildred, Poultry. He was succeeded by his only son, Orlando.
Orlando married Ellen Lancashire, his stepmother's daughter by her first husband. He died without surviving male issue on 14 June 1737, his only son (Robert) having died a few months before on 17 January; the baronetcy became extinct. His widow died on 3 April 1745.