Sir William Fleetwood (1563 – 13 December 1630) was an English politician who sat in the House of Commons at various times between 1584 and 1628.
Fleetwood was the eldest son of William Fleetwood of Great Missenden Buckinghamshire and his wife Marian Barley, daughter of John Barley of Kingsey, Buckinghamshire. He was admitted at Middle Temple in 1584 and was readmitted in 1592 after some dispute. In 1584, Fleetwood was elected Member of Parliament for Preston where his father was recorder. In 1586 he was elected MP for Poole.
Fleetwood succeeded his father to considerable estates including the abbey of Great Missenden in 1594. He became J.P. for Berkshire and Buckinghamshire by 1597. He was surveyor of lands in north parts, duchy of Lancaster in 1603 and was knighted in the same year. In 1604 he was elected MP for Buckinghamshire and was probably elected in 1614. He was elected MP for Buckinghamshire again in 1621 and was High Sheriff of Buckinghamshire from 1622 to 1623. He was re-elected MP for Buckinghamshire in 1624 and again in 1628, and sat until 1629 when King Charles decided to rule without parliament for eleven years.
Fleetwood died at the age of 66 at Great Missenden.
Fleetwood married Anne Barton, daughter of Ralph Barton of Smithhills Lancashire, and had seven sons and seven daughters. His wife died in 1621.