Sir John Glynne KS (1602 – 15 November 1666) was a Welsh lawyer of the Commonwealth and Restoration periods, who rose to become Lord Chief Justice of the Upper Bench, under Oliver Cromwell. He sat in the House of Commons at various times between 1640 and 1660.
John Glynne was born in 1603 at Glynllifon, Carnarvonshire, the eldest son of Sir William Glynne of Glynllifon, a very ancient family that claimed a fanciful descent from Cilmin Droed-tu, founder of one of the 15 tribes of North Wales, by Jane, da. of John Griffith of Carnarvon. Glynne was educated at Westminster School and Hart Hall, Oxford, where he matriculated 9 November 1621, aged 18. He entered Lincoln's Inn on 27 January 1620 and was called to the Bar on 24 June 1628.
In April 1640, Glynne was elected Member of Parliament for Westminster in the Short Parliament. He was re-elected MP for Westminster for the Long Parliament in November 1640. His first major parliamentary triumph was the summing-up of the case against the Earl of Strafford, and he enjoyed a successful career during the commonwealth, becoming a serjeant-at-law, judge of assize, and finally Lord Chief Justice of the Upper Bench, and was a member of the Committee of Both Kingdoms. However, his Presbyterianism put him out of favour of with the army, and he was expelled from Parliament in 1647 and imprisoned in the Tower for almost a year. He was counsel for the University of Cambridge from 1647 to 1660. He returned to Parliament for Caernarvonshire from 1654 to 1655 in the First Protectorate Parliament. In 1656 he was elected MP for both Carnarvonshire and Flintshire in the Second Protectorate Parliament and chose to sit for Flintshire. He was nominated and accepted a seat in Cromwell's Other House.