The Royal Northumberland Fusiliers was an infantry regiment of the British Army. Originally raised in 1674 as the 5th Regiment of Foot, the regiment was amalgamated with three other fusilier regiments in 1968 to form the Royal Regiment of Fusiliers.
The regiment was originally part of the Dutch service and known as the Irish Regiment, or Viscount Clare's Regiment. The regiment was transferred to the British Service on 5 June 1685, establishing its order of precedence as the 5th Regiment of the Line. Until 1751, like most other regiments, it was known successively by the names of the colonels who commanded them at the time.
On 1 August 1782, all those regiments of the line that did not have a special title were given a county designation. The primary purpose was to improve recruiting, but no links were actually formed with the counties after which the regiments.