300px|thumb|Four New Zealand prime ministers pictured in 1992 (from left) – [[David Lange, Jim Bolger, Robert Muldoon and Mike Moore]]
The prime minister of New Zealand is the country's head of government and the leader of the Cabinet, whose powers and responsibilities are defined by convention. The prime minister is always a member of parliament. Since 1935, every prime minister has been a member of either the National party or the Labour party, reflecting their domination of New Zealand politics. After the introduction of mixed-member proportional voting in 1996, prime ministers have usually needed to negotiate agreements with smaller parties to maintain a majority in Parliament. That title remained in use almost exclusively for more than 30 years, until Richard Seddon changed it to "prime minister" during his tenure in the office; he used the title officially at the 1902 Colonial Conference. Most commonly, Henry Sewell, who served during 1856, is regarded as New Zealand's first premier. Beginning with Sewell, 42 individuals have so far held the premiership, not including Hugh Watt, who was acting prime minister following the death of Norman Kirk. Eight prime ministers have held the position for more than one period in office. Richard Seddon, prime minister for thirteen years between 1893 and 1906, held the office for the longest term. The youngest prime minister was Edward Stafford, who assumed office at age 37, and the oldest was Walter Nash, who left office at age 78. Three prime ministers have been women, a count equalled by Finland, Lithuania, Poland and the United Kingdom, and only surpassed by Switzerland.
The current prime minister is Christopher Luxon, who assumed office on 27 November 2023.
List of prime ministers
The parties shown are those to which the heads of government belonged at the time they held office and the electoral districts shown are those they represented while in office. Several prime ministers belonged to parties other than those given and represented other electorates before and after their time in office. A number in brackets indicates the prime minister served a previous term in office.
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Died in office
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|+ Colonial Secretaries (1856–1869)