Carless days was a petrol demand reduction scheme active in New Zealand from July 1979 to May 1980. Introduced by the Third National Government of New Zealand, during the 1979 oil crisis, the scheme prohibited owners of private petrol-powered vehicles to drive on a self-designated day of the week. The enabling regulations were one of several attempts to help the New Zealand economy after the oil shocks of the late 1970s—other such policies included the Think Big strategy.

A drop in oil production in the wake of the Iranian Revolution led to an energy crisis in 1979. Although the global oil supply only decreased by approximately four percent, the oil markets' reaction raised the price of crude oil drastically over the next 12 months, more than doubling it to $39.50 per barrel ($248/m3). The sudden increase in price was connected with fuel shortages and long lines at gas stations similar to the 1973 oil crisis.