Peterhouse is a constituent college of the University of Cambridge in England, founded in 1284 by Hugh de Balsham, Bishop of Ely. Peterhouse has around 300 undergraduate and 175 graduate students, and 54 fellows.

Peterhouse alumni are notably eminent within the natural sciences, including scientists Lord Kelvin, Henry Cavendish, Charles Babbage, James Clerk Maxwell, James Dewar, Frank Whittle, and five Nobel prize winners in science: Sir John Kendrew, Sir Aaron Klug, Archer Martin, Max Perutz, and Michael Levitt. Peterhouse alumni also include Lord Chancellors, Lord Chief Justices, important poets such as Thomas Gray, the first Anglican Bishop of New York Samuel Provoost, the first British Fields Medallist Klaus Roth, Oscar-winning film director Sam Mendes and comedian David Mitchell. British Prime Minister Augustus FitzRoy, 3rd Duke of Grafton, and Elijah Mudenda, second prime minister of Zambia, also studied at the college.

Peterhouse is one of the wealthiest colleges in Cambridge, with assets exceeding £350 million. It is currently third in terms of net assets per student. Members of Peterhouse are encouraged to attend communal dinners, known as "Hall". Hall takes place in two sittings, with the second known as "Formal Hall", which consists of a three-course candlelit meal and which must be attended wearing suits and gowns. At Formal Hall, the students rise as the fellows proceed in, a gong is rung, and two Latin graces are read. Peterhouse also hosts a biennial white-tie ball as part of May Week celebrations.

In recent years, Peterhouse has been ranked as one of the highest achieving colleges in Cambridge, although academic performance tends to vary year to year due to its small population. In the past five years, it has sat in the top ten of the 29 colleges within the Tompkins Table.^[when?] Peterhouse sat at fourth in 2018 and 2019.

The foundation of Peterhouse dates to 1280, when letters patent from Edward I dated Burgh, Suffolk, 24 December 1280 allowed Hugh de Balsham, to keep a number of scholars in the Hospital of St John, where they were to live according to the rules of the scholars of Merton. After disagreement between the scholars and the Brethren of the Hospital, both requested a separation. As a result, in 1284 Balsham transferred the scholars to the present site with the purchase of two houses just outside the then Trumpington Gate to accommodate a Master and fourteen "worthy but impoverished Fellows". The Church of St Peter without Trumpington Gate was to be used by the scholars. Bishop Hugo de Balsham died in 1286, bequeathing 300 marks that were used to buy further land to the south of St Peter's Church, on which the college's Hall was built.

The earliest surviving set of statutes for the college was given to it by the then Bishop of Ely, Simon Montacute, in 1344. Although based on those of Merton College, these statutes clearly display the lack of resources then available to the college. They were used in 1345 to defeat an attempt by Edward III to appoint a candidate of his own as scholar. In 1354–55, William Moschett set up a trust that resulted in nearly 70 acres (280,000 m²) of land at Fen Ditton being transferred to the College by 1391–92. The College's relative poverty was relieved in 1401 when it acquired the advowson and rectory of Hinton through the efforts of Bishop John Fordham and John Newton. During the reign of Elizabeth I, the college also acquired the area formerly known as Volney's Croft, which today is the area of St Peter's Terrace, the William Stone Building and the Scholars' Garden.

In 1553, Andrew Perne was appointed Master. His religious views were pragmatic enough to be favoured by both Mary I, who gave him the Deanery of Ely, and Elizabeth I. A contemporary joke was that the letters on the weathervane of St Peter's Church could represent "Andrew Perne, Papist" or "Andrew Perne, Protestant" according to which way the wind was blowing. Having previously been close to the reformist Regius Chair of Divinity, Martin Bucer, later as vice-chancellor of the university Perne would have Bucer's bones exhumed and burnt in Market Square. John Foxe in his Actes and Monuments singled this out as "shameful railing". There is a hole burnt in the middle of the relevant page in Perne's own copy of Foxe. Perne died in 1589, leaving a legacy to the college that funded a number of fellowships and scholarships, as well bequeathing an extensive collection of books. This collection and rare volumes since added to it is now known as the Perne Library.

Between 1626 and 1634, the Master was Matthew Wren. Wren had previously accompanied Charles I on his journey to Spain to attempt to negotiate the Spanish Match. Wren was a firm supporter of Archbishop William Laud, and under Wren the college became known as a centre of Arminianism. This continued under the Mastership of John Cosin, who succeeded Wren in 1634. Under Cosin significant changes were made to the college's Chapel to bring it into line with Laud's idea of the "beauty of holiness". On 13 March 1643, in the early stages of the English Civil War, Cosin was expelled from his position by a Parliamentary ordinance from the Earl of Manchester. The Earl stated that he was deposed "for his opposing the proceedings of Parliament, and other scandalous acts in the University". On 21 December of the same year, statues and decorations in the Chapel were pulled down by a committee led by the Puritan zealot William Dowsing.