St John's College was founded as a men's college in 1555, it has been coeducational since 1979. Its founder, Sir Thomas White, intended to provide a source of educated Roman Catholic clerics to support the Counter-Reformation under Queen Mary.

St John's is the wealthiest college in Oxford, with assets worth over of £790 million as of 2022, largely due to nineteenth-century suburban development of land in the city of Oxford of which it is the ground landlord.

On 1 May 1555, Sir Thomas White, lately Lord Mayor of London, obtained a Royal Patent of Foundation to create a charitable institution for the education of students within the University of Oxford. White, a Roman Catholic, originally intended St John's to provide a source of educated Roman Catholic clerics to support the Counter-Reformation under Queen Mary, and indeed Edmund Campion, the Roman Catholic martyr, studied here.

White was Master of the Merchant Taylors' Company, and established a number of educational foundations, including the Merchant Taylors' School. 

Female students were first admitted in 1979, after over four centuries of the college as an institution for men only. 

Although primarily a producer of Anglican clergymen in the earlier periods of its history, St John's also gained a reputation for degrees in law, medicine and PPE (Philosophy, Politics and Economics)

St John's College, Oxford - Wikipedia