The Otago and Southland Regiment is a Territorial Force unit of the New Zealand Army. It was originally formed in 1948 by the amalgamation of two separate regiments:
In turn, those two regiments were the heirs of the original 4th (Otago Rifles) Regiment, 10th (North Otago) Regiment, 8th (Southland Rifles) Regiment and 14th (South Otago) Regiment formed in the early 1900s.
The regiment become a TF battalion of the Royal New Zealand Infantry Regiment in 1964 during the reorganisation of the army. This was until the later reorganisation of 1999, which saw the TF battalions split from the RNZIR to become multi-function battalion groups. The Otago and Southland Regiment became the 4th Otago and Southland Battalion Group, with the following unit types:
In December 2012 4th Otago and Southland Battalion Group merged with 2nd Canterbury (Nelson, Marlborough, West Coast) Battalion Group to form 2/4 Battalion.