You can find more detail on these MPs in the Roll of MPs in the NZ House of Representatives, 1854 onwards
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Longest serving member of Parliament: Rex Mason
MP 15 April 1926 - 25 October 1966 (MP for over 40 years)
Longest serving woman member of Parliament: Annette King
MP 14 July 1984 26 October 1990, 6 November 1993 22 September 2017 (MP for 30 years)[i]
Current longest continuously serving members of Parliament (Father and Mother of the House[ii]): Gerry Brownlee and Judith Collins
MPs respectively since 12 October 1996 (MP continuously for over 26 years) and 27 July 2002 (MP continuously for over 21 years).
Shortest serving member of Parliament: Henry Stark
MP 19 February 1861 - 27 April 1861 (MP for 67 days)
Oldest ever member of Parliament: Walter Nash
Died in Office aged 86 years 112 days (MP 1929-1968)
Longest lived member of Parliament: Garnet Mackley
Died 24 April 1986, aged 102 years (MP 1943-1949)
Longest lived Prime Minister: Sir George Grey
Died 20 September 1898, aged 86 years 159 days
Oldest Prime Minister: Walter Nash
Became Prime Minister on 15 December 1957, aged 75
Youngest Prime Minister: Edward Stafford
Became Prime Minister on 2 June 1856, aged 37[iii]
Longest serving Prime Minister: Richard Seddon
1 May 1893 - 10 June 1906 (13 years & 1 month)
Shortest serving Prime Minister: Henry Sewell[iv]
7 May 1856 - 20 May 1856 (14 days)
Oldest member of Parliament at time of their first election: William Cargill
Elected 11 December 1855, aged 71
Current oldest member of Parliament: Winston Peters
First elected 25 November 1978, aged 78 at the 2023 election
Youngest member of Parliament at time of their election: James Stuart-Wortley
Elected 27 August 1853, aged 20 years & 7 months
Current youngest member of Parliament: Hana-Rawhiti Maipi-Clarke
Elected 14 October 2023, aged 21 at the 2023 election
[i] Whetū Tirikātene-Sullivan was an MP for 29 continuous years (1967-1996).
[ii] The title given to the MP who has served the longest without a break.
[iii] Stafford was aged 13,556 days when he became Prime Minister. Jacinda Ardern was aged 13,606 days when she became Prime Minister.
[iv] Sewell served the shortest total time as Prime Minister. Harry Atkinson served the shortest single term (28 Aug to 3 Sept 1884) but he had four terms as Prime Minister, so reached a total of 5 years 116 days