There are numerous gangs in New Zealand, of varying criminality, organisation and ethnicity, including outlaw motorcycle gangs, street gangs and ethnically based gangs. A chapter of the Hells Angels motorcycle club was formed in Auckland in 1961, the first Hells Angels chapter outside the US. Soon after, the Mongrel Mob formed in Hastings and Wellington, developing into a predominantly Māori and Pacific Islander gang, and having the largest membership in the country. Through the 1960s and 1970s, other outlaw motorcycle clubs and ethnically based gangs formed, including another predominantly Māori gang, Black Power, which grew to rival the Mongrel Mob.

A gang is a group or society of associates, friends, or members of a family with a defined leadership and internal organization that identifies with or claims control over territory in a community and engages, either individually or collectively, in illegal, and possibly violent, behavior, with such behavior often constituting a form of organized crime.