With an antecedence reaching back to 1689, the regiment was formed in 1992. The creation followed the Options for Change proposals which recommended through the amalgamation of the Royal Irish Rangers and the Ulster Defence Regiment (UDR). Most of the membership of the new Regiment came from the UDR. This produced a regiment with eleven battalions:

The Home Service battalions, permanently based in Northern Ireland, filled the role formerly occupied by the UDR, conducting counter-terrorism operations in Northern Ireland under Operation BANNER. The 1st and 2nd Battalions could serve worldwide as general service battalions.

Because of its size, the regiment was removed from the King's Division and existed outside the divisions of infantry. In 1993, the two regular battalions were amalgamated as 1 R IRISH. In 2001, the number of Home Service battalions reduced to three.