Robert Wallop (20 July 1601 – 19 November 1667) was an English politician who sat in the House of Commons at various times from 1621 to 1660. He supported the Parliamentary cause in the English Civil War and was one of the regicides of King Charles I of England.
Wallop was the only son of Sir Henry Wallop of Farleigh Wallop, Hampshire and his wife Elizabeth Corbet, daughter of Robert Corbet, of Morton Corbet, Shropshire.
In 1621, Wallop was elected Member of Parliament for Andover and was re-elected for the seat in 1624. In 1625 he was elected MP for Hampshire and was re-elected for the seat again in 1626. He was re-elected MP for Andover in 1628 and sat until 1629, when King Charles decided to rule without parliament for eleven years.
Wallop refused to contribute towards the Bishops' War in 1639 and 1640 out of antipathy to the King. In April 1640 he was elected MP for Andover for the Short Parliament and was re-elected MP for Andover for the Long Parliament in November 1640. He supported parliament in the Civil War joining in all the subsequent votes against King Charles.
Nevertheless, the King had such confidence in Wallop's honour, that in 1645 he said to Parliament he should be willing to put the militia into Wallop's hands, with many noblemen, and others, upon such terms as his commissioners at Uxbridge had agreed upon. However this proposal was rejected. Wallop survived Pride's Purge to sit in the Rump Parliament and was named by the army grandees as one of the 59 Commissioners who sat in judgment at the trial of Charles I. He attended the trial and sat in the Painted Chamber 15 January and on 22 January, and in Westminster Hall the same day and on 23 January, but he did not sign the death warrant.