Barnwell Castle is a ruined castle, south of the town of Oundle

Oundle

Oundle is an ancient market town on the River Nene in Northamptonshire, England, with a population of 5,345 or 5,674 . It lies some north of London and south-west of Peterborough...

, and west of the village of Barnwell, Northamptonshire

Barnwell, Northamptonshire

Barnwell is a village in the district of East Northamptonshire in England, south of the town of Oundle, north of London and south-west of Peterborough...

 . It has been designated by English Heritage

English Heritage

English Heritage . is an executive non-departmental public body of the British Government sponsored by the Department for Culture, Media and Sport...

 as a Grade I listed building, and is a Scheduled Ancient Monument

Scheduled Ancient Monument

In the United Kingdom, a scheduled monument is a 'nationally important' archaeological site or historic building, given protection against unauthorized change. The various pieces of legislation used for legally protecting heritage assets from damage and destruction are grouped under the term...

.

A motte and bailey castle was erected in 1132. The stone castle was built during the reign of King Henry III

Henry III of England

Henry III was the son and successor of John as King of England, reigning for 56 years from 1216 until his death. His contemporaries knew him as Henry of Winchester. He was the first child king in England since the reign of Æthelred the Unready...

 by the family of Berengar Le Moyne. In the English Civil War

English Civil War

The English Civil War was a series of armed conflicts and political machinations between Parliamentarians and Royalists...

 it was used by its owner, Sir Edward Montagu

Edward Montagu, 1st Baron Montagu of Boughton

Edward Montagu, 1st Baron Montagu of Boughton was an English politician. He was one of the key founders of what is known today as Guy Fawkes Night through his sponsorship, in Parliament, of the Observance of 5th November Act 1605. His support for King Charles I led to his arrest in August 1642...

, as an arsenal

Arsenal

An arsenal is a place where arms and ammunition are made, maintained and repaired, stored, issued to authorized users, or any combination of those...

 for the Royal

Cavalier

Cavalier was the name used by Parliamentarians for a Royalist supporter of King Charles I and son Charles II during the English Civil War, the Interregnum, and the Restoration...

 cause. After the civil war the Montagu family built a substantial manor house, Barnwell Manor

Barnwell Manor

Barnwell Manor is the historic former home of the Duke and Duchess of Gloucester. It is located by the village of Barnwell, near Oundle, Northamptonshire in England.-The house and estate:...

, near the castle.

Substantial parts of the castle remain. It is quadrilateral in shape with cylinder towers on the northeast, northwest and southwest corners. On the southeast corner is a twin-towered gatehouse. The walls are up to 30 feet (9 m) high and over 12 feet (4 m) thick.

The castle is privately owned and access is not permitted.