This is a list of prime ministers of New Zealand by age, including when they were born, what age they were when they were appointed prime minister, what age they were when they left the office and the age at which they died, or their current age as of 6 April 2024 if they are still alive. The table can be sorted by each different category.

The date of appointment is the date on which they were sworn in by the governor-general for their first term. The day on which they departed office is the final day of their final term. This is either the day a new prime minister was appointed or their date of death if they died whilst in office.

The oldest living prime minister is Jim Bolger, born 31 May 1935 (aged 88 years, 311 days). The youngest living former prime minister is Jacinda Ardern, born 26 July 1980 (aged 43 years, 255 days).

The longest-lived prime minister is also Jim Bolger who is currently aged 88 years, 311 days. George Grey was the second longest-lived prime minister who lived to the age of 86 years, 158 days. Bolger surpassed Grey's lifespan on 6 November 2021. The second oldest-living prime minister, Geoffrey Palmer, will tie Grey if he lives to 27 September 2028. The shortest-lived prime minister was Norman Kirk, who died in office at the age of 51 years, 237 days.

The prime minister with the longest retirement is Robert Stout. He left office on 8 October 1887, and died 42 years, and 284 days later on 19 July 1930. The prime minister with the shortest retirement is Joseph Ward, who died on 8 July 1930, 41 days after he left office on 28 May 1930.

Key:

The three youngest people when they first became prime minister were:

• Edward Stafford – 37
• Jacinda Ardern – 37
• Julius Vogel – 38

The three oldest people when they first became prime minister were:

• Walter Nash – 75
• Francis Bell – 74
• George Grey – 65

The three oldest people to last leave the office of prime minister were:

• Walter Nash – 78
• Francis Bell – 74
• Joseph Ward – 74

The three youngest people to last leave the office of prime minister were:

• Julius Vogel – 41
• Mike Moore – 41
• Frederick Weld – 42

Not all prime ministers live to become the oldest of their time. Of the 33 deceased prime ministers, 16 eventually became the oldest of their time, while 17 did not (including all 5 prime ministers who died in office, and 12 others). Jim Bolger has held this distinction since Bill Rowling's death on 31 October 1995 a record 28 years, 158 days so far. He surpassed the previous record held by Robert Stout on 24 November 2018. Robert Stout became the oldest living prime minister when John Hall died in 1907 and remained so until his death in 1930, for 23 years and 24 days.

John Hall became the oldest living prime minister after the death of George Waterhouse, but he survived Waterhouse by only 323 days. On one occasion the oldest living prime minister lost this distinction not by his death, but due to the appointment of a prime minister who was older. Sidney Holland ceased to be the oldest living prime minister when Walter Nash was appointed.

John Hall was the oldest to acquire this distinction at the age of 81 years, and 231 days. Francis Bell, who was 84 years, and 348 days old when he died, was the oldest prime minister to die without ever acquiring this distinction. Mike Moore, who died on 2 February 2020 at 71 years, and 5 days old is the most recent prime minister to die without ever acquiring this distinction.

Wikimedia Commons has media related to Prime ministers of New Zealand.

• List of prime ministers of New Zealand by place of birth