In the British Army, there have been two regiments to be titled the Royal Irish Regiment

Royal Irish Regiment

The Royal Irish Regiment was formed in 1684 by the Earl of Granard from independent companies in Ireland. In 1695, the regiment became known as the Royal Regiment of Ireland before being ranked as the 18th Regiment of Foot. In 1881 it became the Royal Irish Regiment, and served as the county regiment of Tipperary, Wexford and Kilkenny. The regiment was one of those disbanded following the establishment of the Irish Free State in 1922.

Royal Irish Regiment (27th (Inniskilling), 83rd and 87th and Ulster Defence Regiment

The Royal Irish Regiment (27th (Inniskilling) 83rd and 87th and Ulster Defence Regiment) is an infantry regiment of the British Army. Aside from the Irish Guards, the Royal Irish Regiment is the only remaining wholly Irish regiment in the army. It was formed in 1992 under the Options for Change proposals through the amalgamation of the Royal Irish Rangers and the Ulster Defence Regiment. This produced a regiment with a total of eleven battalions:

• Regular Army
  • 1st Battalion, Royal Irish Regiment
  • 2nd Battalion, Royal Irish Regiment
• Territorial Army
  • 4th Battalion, Royal Irish Rangers
  • 5th Battalion, Royal Irish Rangers
• Home Service
  • 3rd (County Down) Battalion, Royal Irish Regiment
  • 4th (County Fermanagh and County Tyrone) Battalion, Royal Irish Regiment
  • 5th (County Londonderry) Battalion, Royal Irish Regiment
  • 6th (County Armagh) Battalion, Royal Irish Regiment
  • 7th (City of Belfast) Battalion, Royal Irish Regiment
  • 8th (County Tyrone) Battalion, Royal Irish Regiment
  • 9th (County Antrim) Battalion, Royal Irish Regiment

The Home Service battalions were those of the Ulster Defence Regiment, purely for security in Northern Ireland, while the regular army units were standard general service battalions. However, because of its new circumstances (responsibility for home service in Ulster), the regular battalions were removed from the Royal Irish Rangers previous position in the King's Division, and the new regiment was made a corps in its own right. In 1993, one of the regular battalions was disbanded, while the 3rd and 6th battalions merged, as did the 4th and 5th battalions of the Royal Irish Rangers to form 4th/5th Battalion. In 2001, the number of home service battalions was reduced to three:

• 2nd Battalion - amalgamation of 7th and 9th Battalions
• 3rd Battalion - amalgamation of 3rd and 8th Battalions
• 4th Battalion - amalgamation of 4th and 5th Battalions

Today, the operational command of the Royal Irish Regiment encompasses:

• 1st Battalion - general service
• 2nd Battalion - home service
• 3rd Battalion - home service
• 4th Battalion - home service
• The Royal Irish Rangers - Territorial Army
• The North Irish Horse - this is a Royal Armoured Corps TA squadron that is part of the Queen's Own Yeomanry, but is under the operational command of the Royal Irish Rangers

As a consequence, it shares with the Parachute Regiment the title of largest infantry regiment in the British Army.

In 2004, a major restructuring of the infantry was announced, with all of the remaining single battalion infantry regiments being amalgamated together. Under normal circumstances, this may have put the Royal Irish Regiment at risk. However, because of its unique status in providing the home defence for Northern Ireland, plus the fact that it is the only remaining Irish infantry regiment, it was decided to leave the Royal Irish Regiment as it was, with no changes, with perhaps the exception of bringing the TA battalion more fully within the regiment's structure (i.e. renaming it as 5th Battalion, Royal Irish Regiment). This allows a 'line infantry footprint' to remain in Northern Ireland.