John Berkeley, 1st Baron Berkeley of Stratton (1602 – 26 August 1678) was an English royalist soldier, of the Bruton branch of the Berkeley family. From 1648 he was closely associated with James, Duke of York, and rose to prominence, fortune, and fame. He and Sir George Carteret were the founders of the Province of New Jersey, a British colony in North America that would eventually become the U.S. state of New Jersey.
Berkeley was the second son of Sir Maurice Berkeley and his wife Elizabeth Killigrew, daughter of Sir Henry Killigrew of Hanworth. His elder brother was Charles Berkeley, 2nd Viscount Fitzhardinge; his younger brother, Sir William Berkeley, served as royal governor of the colony of Virginia from 1642 to 1652 and again from 1660 to 1677. John Berkeley was accredited ambassador from Charles I of England to Christina of Sweden, in January 1637, to propose a joint effort by the two sovereigns for the reinstatement of the elector palatine in his dominions; probably the employment of Berkeley in this by his cousin, Sir Thomas Roe, who had conducted negotiations between Gustavus Adolphus and the king of Poland. Berkeley returned from Sweden in July 1637. He had a commission in the army against the Scots in 1638, and was knighted at Berwick in that year. In 1640 he was returned to parliament for both Heytesbury and Reading, electing to retain his seat for the former place. Next year he was accused in parliament of complicity in the Army Plots, expelled from the house, and committed to the Tower of London; he was subsequently bailed by Edward Sackville, 4th Earl of Dorset and Henry Grey, 1st Earl of Stamford in the sum of £10,000, but the outbreak of hostilities prevented any further steps being taken.