Deddington is a civil parish and small town in Oxfordshire about 6 miles (10 km) south of Banbury. The parish includes two hamlets: Clifton and Hempton. The 2011 Census recorded the parish's population as 2,146.

Deddington is a small settlement but has a commercial centre including a market place, which hosts a popular monthly farmer’s market. It has been a market town probably since the 12th century. One of the Hundred Rolls of King Edward I from 1275-76 records Deddington as a borough. It has a deli, coffee shop, restaurant, three pubs and a town hall. Its football team is called Deddington Town FC.

The toponym is derived from the Old English for "place of the people of Dæda". "Dæda" was short for Anglo-Saxon names such as Dædheah. The toponym was spelt Dadintone around AD 950, Dædintun around 1050 and Dadinton in 1190.

After the Norman conquest of England in 1066, William the Conqueror's step-brother Odo, Bishop of Bayeux, held the manor of Deddington. Odo had the outer bailey of Deddington Castle built in what is now the east of the town. The inner bailey on the east side of the castle seems to have been inserted in the 12th century, and buildings within the inner bailey seem to have been added later that century.

In the 13th century the castle declined and fell into disrepair. In the 14th it was demolished and its building stone re-used. In 1377 some of the stone was sold to Bicester Priory. There have been two archaeological excavations at the site, in 1947 and in 1978. The remains were reburied afterward and only the extensive earthworks are visible today.

On 9 June 1312 the Earl of Pembroke was escorting Piers Gaveston, Earl of Cornwall south after Gaveston's surrender to a group of rebellious earls at Scarborough Castle. The party stopped to rest at an inn in Deddington. Pembroke had guaranteed Gaveston's safety to the king on pain of forfeiting his lands, but he left Gaveston at Deddington and went to visit his wife at Bampton Castle, about 25 miles (40 km) away.

The Earl of Warwick with his men surrounded the inn and Gaveston, seeing that his guards would not fight, had to come outside to be chained and thrown in prison. A few days later Gaveston was taken to Warwick to be tried by the other earls and condemned to death. On 19 June he was taken to Blacklow Hill by the Earl of Lancaster and hacked to death by two Welshmen. This event is recalled by a chained eagle in Deddington's coat of arms.