Sir John St Barbe, 1st Baronet (c. 1655 – 7 September 1723), of Ashington, Somerset and Broadlands, Hampshire, was Member of Parliament for Ilchester in 1681. He was created a baronet on 30 December 1662 at the age of 7.
He was the second son of John St Barbe of Broadlands, MP for Hampshire in 1654 and a Parliamentarian in the Civil War, by his wife Grissell Pynsent, daughter of John Pynsent of Carleton-Curliew, Leicestershire and of Combe, Surrey, Prothonotary of Common Pleas. His ancestors had been seated at Ashington, near Ilchester, in Somerset, since the 14th century, and in the late 16th century inherited Broadlands in Hampshire by marriage to the heiress.
In 1661 his elder brother died and John became heir to his father. In 1671 he matriculated at Magdalene College, Cambridge. In 1674 he entered the Inner Temple as a student of law. he was elected Member of Parliament for Ilchester in 1681 and served as Sheriff of Hampshire 1703-4.
He married twice but left no children:
He died on 7 September 1723 and as he left no children he appointed his great-great-nephew Humphrey Sydenham (1694–1757) of Combe near Dulverton in Somerset as his sole heir and executor, who named his own son St Barbe Sydenham. The Sydenham inheritance included the manors of Broadlands and Marston Magna.