Oriel College (/ˈɔːriəl/) is a constituent college of the University of Oxford in Oxford, England. Located in Oriel Square, the college has the distinction of being the oldest royal foundation in Oxford (a title formerly claimed by University College, whose claim of being founded by King Alfred is no longer promoted). In recognition of this royal connection, the college has also been historically known as King's College and King's Hall. The reigning monarch of the United Kingdom (since 2022, Charles III) is the official visitor of the college.

The original medieval foundation established in 1324 by Adam de Brome, under the patronage of King Edward II of England, was the House of the Blessed Mary at Oxford, and the college received a royal charter in 1326. In 1329, an additional royal grant of a manor house, La Oriole, eventually gave rise to its common name. The first design allowed for a provost and ten fellows, called "scholars", and the college remained a small body of graduate fellows until the 16th century, when it started to admit undergraduates. During the English Civil War, Oriel played host to high-ranking members of the king's Oxford Parliament.

The main site of the college incorporates four medieval halls: Bedel Hall, St Mary Hall, St Martin Hall, and Tackley's Inn, the last being the oldest standing medieval hall in Oxford. The college has nearly 40 fellows, about 300 undergraduates and some 250 graduates. Oriel was the last of Oxford's men's colleges to admit women, doing so in 1985 after more than six centuries as an all-male institution. Today, however, the student body has almost equal numbers of men and women. Oriel's notable alumni include two Nobel laureates; prominent fellows have included founders of the Oxford Movement. Among Oriel's more notable possessions are a painting by Bernard van Orley and three pieces of medieval silver plate. As of the 2020–21 academic year^[update], the college was ranked twentieth in academic performance out of thirty colleges in the Norrington Table, having topped the table in 2015–16.

On 24 April 1324, the Rector of the University Church, Adam de Brome, obtained a licence from King Edward II to found a "certain college of scholars studying various disciplines in honour of the Virgin" and to endow it to the value of £30 a year. Brome bought two properties in 1324, Tackley's Hall, on the south side of the High Street, and Perilous Hall, on the north side of Broad Street, and as an investment, he also purchased the advowson of a church in Aberford.

Brome's foundation was confirmed in a charter dated 21 January 1326, in which the Crown, represented by the Lord Chancellor, was to exercise the rights of Visitor; a further charter drawn up in May of that year gave the rights of Visitor to Henry Burghersh, Bishop of Lincoln, as Oxford at that time was part of the diocese of Lincoln. Under Edward's patronage, Brome diverted the revenues of the University Church to his college, which thereafter was responsible for appointing the Vicar and providing four chaplains to celebrate the daily services in the church. The college lost no time in seeking royal favour again after Edward II's deposition, and Edward III confirmed his father's favour in February 1327, but the amended statutes with the Bishop of Lincoln as Visitor remained in force. In 1329, the college received by royal grant a large house belonging to the Crown, known as La Oriole, on the site of what is now First Quad. It is from this property that the college acquired its common name, "Oriel"; the name was in use from about 1349. The word referred to an oratoriolum, or oriel window, forming a feature of the earlier property.

In the early 1410s several fellows of Oriel took part in the disturbances accompanying Archbishop Arundel's attempt to stamp out Lollardy in the university; the Lollard belief that religious power and authority came through piety and not through the hierarchy of the Church particularly inflamed passions in Oxford, where its proponent, John Wycliffe, had been head of Balliol. Disregarding the provost's authority, Oriel's fellows fought bloody battles with other scholars, killed one of the Chancellor's servants when they attacked his house, and were prominent among the group that obstructed the Archbishop and ridiculed his censures.

In 1442, Henry VI sanctioned an arrangement whereby the town was to pay the college £25 a year from the fee farm (a type of feudal tax) in exchange for decayed property, allegedly worth £30 a year, which the college could not afford to keep in repair. The arrangement was cancelled in 1450.

In 1643, a general obligation was imposed on Oxford colleges to support the Royalist cause in the English Civil War. The King called for Oriel's plate, and almost all of it was given, the total weighing 29 lb. 0 oz. 5 dwt. of gilt, and 52 lb. 7 oz. 14 dwt. of "white" plate. In the same year the college was assessed at £1 of the weekly sum of £40 charged on the colleges and halls for the fortification of the city. When the Oxford Parliament was assembled during the Civil War in 1644, Oriel housed the executive committee of the Privy Council, Parliament being held at neighbouring Christ Church. Following the defeat of the Royalist cause, the university was scrutinised by the Parliamentarians, and five of the eighteen Oriel fellows were removed. The Visitors, on their own authority, elected fellows between 1648 and October 1652, when without reference to the Commissioners, John Washbourne was chosen; the autonomy of the college in this respect seems to have been restored.