De Keyser, William (c.1603–p.1685), sculptor and architect, was born in Amsterdam, the Netherlands, one of four sons of Hendrik de Keyser, an architect and sculptor in Amsterdam; all four sons trained with their father in the family workshop. An elder sister, Maria, married the English master mason Nicholas Stone (1613), and it is likely that De Keyser went to England to work for his brother-in-law (1621). There is not much evidence of his work in England, although some monumental sculpture of this period is attributed to him. During his stay in England he married Walburga Parker. He was back in Amsterdam in 1640, but there is evidence that he returned to England some years later (1661) as he received a payment of £2 for a drawing for a proposed palace at Greenwich for King Charles II (never executed to his design). In London (1678), he was accepted into the Masons' Company as a ‘foreign member’.
William De Keyser, or possibly a son of his of the same name, came to Ireland to work for the duke of Ormond (qv). He was commissioned, on the recommendation of the duke's agent in London, the earl of Longford (qv), to design and build fountains for Kilkenny castle (c.1681). He also carried out work for the corporation of Dublin and was requested to make two Portland stone sculptures of Charles I and II (1683) to fill the niches, recessed above the Tuscan columns that fronted the Tholsel building on Skinners Row, Dublin (latterly Christchurch Place). This building was a meeting place for Dublin corporation and served a number of other useful civic purposes. Unfortunately the sculptures were too short and he had to make pedestals, two feet high, in order to give the figures the required height. He was paid £100 for the pair and £20 extra for the pedestals (1685). James Malton (qv) has left a valuable representation of the Tholsel, with the statues installed (1796), in his Views of Dublin (1792–7). When the building fell into disrepair and was finally demolished (1805), the sculptures were removed to the north transept, and in 1871 to the crypt in Christ Church cathedral, where they can still be seen. They carry the distinction of being the oldest secular statues in Dublin. It is possible that De Keyser received further commissions from Irish patrons, or perhaps returned to England and worked, but there are no surviving records. The whereabouts and date of his death are unknown.