Sir Arthur Onslow, 1st Baronet (1622 – 21 July 1688) was an English politician who sat in the House of Commons at various times between 1641 and 1685.
Onslow was the eldest son of Sir Richard Onslow and was baptised on 23 April 1622. His father was an important Parliamentarian from Surrey during the Civil War. Onslow was educated at Queen's College, Oxford in 1639 and at Lincoln's Inn in 1640.
In 1641, Onslow was elected Member of Parliament for Bramber in the Long Parliament. He took an active role in political affairs during the English Civil War. In 1654 he was elected MP for Surrey in the First Protectorate Parliament and was re-elected in 1656 for the Second Protectorate Parliament, and in 1659 for the Third Protectorate Parliaments. In 1660, he was elected MP for Guildford in the Convention Parliament. He was re-elected MP for Surrey in 1661 for the Cavalier Parliament.
On 8 May 1674, Onslow obtained a patent in reversion to succeed to his father-in-law Thomas Foote's baronetcy upon his death without heirs, with the precedence of the original creation. He became, therefore, a baronet upon Foote's death in 1687, but died less than a year later, and was succeeded by his eldest son Richard.
Onslow's first wife was Rose Stoughton (d. 1647), daughter of Nicholas Stoughton, by whom he had no children. His second wife was Mary Foote, daughter of Sir Thomas Foote, a wealthy London grocer created a baronet in 1660. By her he had several children, including:
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