1st (County Antrim) Battalion, Ulster Defence Regiment (1 UDR) was formed in 1970 as part of the 7 original battalions specified in The Ulster Defence Regiment Act 1969, which received Royal Assent on 18 December 1969 and was brought into force on 1 January 1970. It was amalgamated with the 9th Battalion, Ulster Defence Regiment in 1984 to form the 1st/9th Battalion, Ulster Defence Regiment.
1st (County Antrim) Battalion, Ulster Defence Regiment combined with another battalion to form one Battalion.