Westminster School is a public school in Westminster, London, England, in the precincts of Westminster Abbey. It derives from a charity school founded by Westminster Benedictines before the 1066 Norman Conquest, as documented by the Croyland Chronicle and a charter of King Offa. Continuous existence is clear from the early 14th century. Its academic results place it among the top schools nationally; about half its students go to Oxbridge, giving it the highest national Oxbridge acceptance rate.

Boys join the Under School at seven and Senior School at 13 by examination. Girls join the Sixth Form at 16. About a quarter of the 750 pupils board. Weekly boarders may go home after Saturday morning school. The school motto, Dat Deus Incrementum, quotes 1 Corinthians 3:6: "I planted the seed... but God made it grow." Westminster was one of nine schools examined by the 1861 Clarendon Commission and reformed by the Public Schools Act 1868.

The school has produced three Nobel laureates: Edgar Adrian (Nobel Prize for Physiology in 1932), Sir Andrew Huxley (likewise in 1963) and Sir Richard Stone (Nobel Prize in Economics in 1984). In the mid-17th century, the liberal philosopher of the Enlightenment, John Locke, attended the school, and seven UK prime ministers also then attended, all belonging to the Whig or Liberal factions of British politics: Henry Pelham and his brother the Duke of Newcastle, the Marquess of Rockingham, James Waldegrave, the Duke of Grafton, the Duke of Portland, and Lord John Russell.