|100 (Yeomanry) Regiment Royal Artillery|
|Garrison/HQ||Army Reserve Centre, Luton|
|Equipment||L118 Light Gun|
100 (Yeomanry) Regiment Royal Artillery was part of the Army Reserve and had sub-units throughout the South of England. It had three gun batteries all equipped with the L118 Light Gun. The regiment's original role was British Army of the Rhine (BAOR) emergency reinforcement, emphasised by its transfer into 49 Infantry Brigade under part of 2 Division. Under 'Options for Change', the regiment became a general support unit fitted out with the FH-70 155mm towed howitzer and assigned to 3 Division; in 1999, it was reassigned as a CS (Close Support) Regiment, losing its ability to deploy as a whole unit. Under Army 2020, it was placed in suspended animation.
The regiment was formed as 100th (Eastern) Medium Regiment Royal Artillery at Grove Park in London in 1967. Its sub-units were RHQ, HQ (Home Counties) Battery at Grove Park, 200 (Sussex Yeomanry) Medium Battery at Brighton, 201 (Hertfordshire and Bedfordshire Yeomanry) Medium Battery at Luton, 202 (Suffolk and Norfolk Yeomanry) Medium Battery at Bury St Edmunds and REME LAD which expanded into a workshop during the FH70 period. In 1970 it became 100th Regiment Royal Artillery and in 1976 it became 100 (Yeomanry) Field Regiment Royal Artillery. In 1993 200 Battery left the regiment and 307 (South Nottinghamshire Hussars) Battery at Bulwell joined the unit. It was renamed 100 (Yeomanry) Regiment Royal Artillery in 1993 and in 1999, HQ and 202 Batteries left the regiment; 202 was replaced by 266 (Gloucestershire Volunteer Artillery) Battery at Bristol.
The batteries were as follows:
- 201 (Hertfordshire and Bedfordshire Yeomanry), based in Luton, was placed in suspended animation under Army 2020.
- 266 (Gloucestershire Volunteer Artillery), based in Bristol, used the 105mm Light Gun in support of 29th Commando Regiment Royal Artillery. Under Army 2020, this battery was subordinated to the 104th Regiment Royal Artillery, and re-roled to mini unmanned air systems.
- 307 (South Nottinghamshire Hussars) Battery, based in Bulwell, was placed in suspended animation under Army 2020.
- King Carl XVI Gustaf of Sweden until 2001 (Moved to 106 Regt)
- Major General Freddie Viggers, ? to 17 February 2001 
- Major General Andrew Ritchie, 17 February 2001 to present
- "Royal Regiment of Artillery, Volunteer Regiments". Archived from the original on 15 March 2004. https://web.archive.org/web/20040315024235/http://www.win.tue.nl/~drenth/BritArmy/Lineage/RA/. Retrieved 11 May 2014.
- Summary of Reserve Structure and Basing Changes Archived 2013-08-10 at the Wayback Machine.
- "100 Regiment RA". Ministry of Defence. Archived from the original on 23 October 2013. https://web.archive.org/web/20131023001138/http://www.army.mod.uk/artillery/23445.aspx. Retrieved 11 May 2014.
- "No. 56164". 2 April 2001. p. 4052. https://www.thegazette.co.uk/London/issue/56164/supplement/4052