Sir Richard Onslow (1601 – 19 May 1664) was an English politician who sat in the House of Commons at various times between 1628 and 1664. He fought on the Parliamentary side during the English Civil War. He was the grandson of one Speaker of the House of Commons and the grandfather of another, both also called Richard Onslow.
Onslow was the son of Sir Edward Onslow of Knowle, Cranleigh and his wife Isabel Shirley, daughter of Sir Thomas Shirley of Wiston, Sussex. He was baptised on 30 July 1601. He was educated at Jesus College, Cambridge in 1617 and at Lincoln's Inn in 1618. He was knighted on 2 June 1624. In 1628 he was elected Member of Parliament for Surrey, and sat until 1629 when King Charles decided to rule without parliament for eleven years. He was also elected MP for Surrey in April 1640 for the Short Parliament and om November 1640 for the Long Parliament. When the Civil War broke out in 1642, he raised a regiment for Parliament, and in 1644 led his men at the siege of Basing House.
Being of moderate views, he was one of the members excluded from Parliament in Pride's Purge in December 1648. In 1654 he was elected again MP for Surrey in the First Protectorate Parliament. He was re-elected MP for Surrey in 1656 for the Second Protectorate Parliament. In 1658 he was elevated to Cromwell's new House of Peers. He returned to the Commons in April 1660 as MP for Guildford in the Convention Parliament, where he worked closely with his more influential friend Sir Anthony Ashley-Cooper to bring about the Restoration. He was re-elected MP for Guildford in 1661 for the Cavalier Parliament and sat until his death in 1664. He was buried at Cranleigh, Surrey.