Peter Sainthill (8 July 1593 – 12 August 1648) was an English politician who sat in the House of Commons from 1640 to 1644. He was a strong supporter of the Royalist side in the English Civil War.
Sainthill was born at Bradninch, Devon, the son of Peter Sainthill of Bradninch House. He was educated at the Free Grammar School at Tiverton (Blundell's School) and was recorder of Tiverton.
In April 1640, Sainthill was elected Member of Parliament for Tiverton in the Short Parliament. He was re-elected in November 1640 for the Long Parliament but supported the king and was disabled from sitting in January 1644. In July 1644 Sainthill entertained King Charles at Bradninch and lent him money for his campaigns.
Sainthill went to Livorno in Italy in 1646 to stay with his brother Robert Sainthill who was agent for the Duke of Tuscany. He died at Livorno at the age of 55.
Sainthill married Dorothy Parker, daughter of Robert Parker and his wife Mary on 12 May 1614 at Bradninch, Devon.