John Foster, 1st Baron Oriel (1740 - 23 August 1828) was an Irish politician.

He was the son of Anthony Foster of Louth, an Irish judge. He was returned to the Irish parliament in 1761, and made his mark in financial and commercial questions, being appointed chancellor of the Irish exchequer in 1784. His law giving bounties on the exportation of corn and imposing heavy taxes on its importation is noted by Lecky as responsible for making Ireland an arable instead of a pasture country. In 1785 he became Speaker.

He opposed the Union, and ultimately refused to surrender the Speaker's mace, which was kept by his family. He was returned to the united parliament, and in 1804 became chancellor of the Irish exchequer under Pitt. In 1821 he was created a peer of the United Kingdom as Baron Oriel of Ferrard in the county of Louth, and died on the 23rd of August 1828.

His wife (d. 1824) had in 1790 been created an Irish peeress, as Baroness Oriel, and in 1797 Viscountess Ferrard; and their son, Thomas Henry (1772-1843), who married Viscountess Massereene (in her own right) and took the name of Sheffington, inherited all these titles; the later Viscounts Massereene being their descendants.