Sir Oliver Cromwell (c. 1566–1655) was an English landowner, lawyer and politician who sat in the House of Commons at various times between 1589 and 1625. He was the uncle of Oliver Cromwell, the Member of Parliament, general, and Lord Protector of England.
Cromwell was the heir of Sir Henry Williams alias Cromwell of Hinchingbrooke and his wife Joan, daughter of Sir Ralph Warren, Lord Mayor of London. He matriculated from Queens' College, Cambridge at Lent 1579 and was admitted at Lincoln's Inn on 12 May 1582. He lived at Godmanchester until the death of his father.
Cromwell held a number of local offices: In 1585 he was captain of musters for Huntingdonshire and at the time of the Spanish Armada he was in charge of the men raised in Huntingdonshire. He was recorder of Huntingdon in 1596. He was Sheriff of Cambridgeshire and Huntingdonshire from 1598 to 1599 and while Sheriff, in 1598, Queen Elizabeth my have dubbed him a knight bachelor.
He was JP from about 1585 but was removed in 1587, when there was one of the periodic purges of justices. In 1594 he was restored to his position as J.P.; as the online History of Parliament observes: "It was felt that in a county as small as Huntingdonshire, the custom by which only one member of a family could be a justice was inapplicable — particularly in the case of the owners of Hinchingbrooke."
Cromwell was first elected Member of Parliament for Huntingdonshire in 1589. He was re-elected to each Parliament up to and including the Addled Parliament of 1614 (that is, in 1593, 1597, 1601, 1604, and 1614). In 1621, the seat was occupied by Richard Beavill, but Sir Oliver stood for and was elected to the Happy Parliament of 1624, and its successor, the Useless Parliament of 1625, after the dissolution at King James' death.