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|Administrator||New Zealand Cricket|
|Number of teams||6|
|Current champion||Auckland Aces|
The competition was instigated in 1906 with the donation of a shield by William Plunket, 5th Baron Plunket, the Governor-General of New Zealand. In its early years, the competition was decided by a series of challenge matches between five provincial cricket association sides: Auckland, Wellington, Canterbury, Otago and, on just two occasions, Hawke's Bay. The first winner was Canterbury.
A proposal in 1912 that the Shield should be decided by an inter-provincial tournament rather than by the challenge system was rejected as impracticable at the time. However, starting with the 1921–22 season, the four principal teams (minus Hawke's Bay, which lost first-class status) played each other in a single round-robin series of matches. Central Districts entered the competition in 1950-51, and Northern Districts in 1956-57.
Shell Oil became principal sponsor in 1974–75 and a new trophy was introduced. Games were played over three days during this period, with an over-limit on the first innings. In latter years the format was experimented with, introducing a shorter second round, various bonus points systems, and eventually a knockout final.
The format and the principal sponsor were changed in 2001–02 season. State Insurance (more commonly just called 'State') replaced Shell Oil. The competitions were renamed to reflect the new sponsor's name, so despite the fact that New Zealand does not have political 'states', the correct name for the first class cricket competition was the 'State Championship'.
Between November and early April, each of the provincial teams play in a one round round-robin series of 4-day matches against every other team. With a target of 112 overs (6.5 hours) daily play, games are only marginally shorter than a typical test match (90 overs/day). Points are awarded based on the results of the matches, and after each team has played each other once, the two highest ranked teams play a 5-day final, in early April.
A limited 50 over competition known as the State Shield was run from late December to the end of January, culminating with a semifinal (2v3) and final (the semifinal winner against the top qualifier) early in February.
In 2006, a provincial Twenty20 competition was begun, and was played over one month during February and into early March each year. The top two sides qualified for that final. It was called the State Twenty20.
Plunket Shield reinstated
With State Insurance withdrawing from their sponsorship, the Plunket Shield was reinstated for the 2009–10 season. New Zealand Cricket has stated that the naming rights are no longer for sale and that the name Plunket Shield will remain. The final has also been abolished, meaning that the champion of the competition will be determined by the points leader at the end of the double round robin.
(counted since 1921–22 season)
|Auckland Aces (Auckland)||1906/07||2015/16||23|
|Wellington Firebirds (Wellington)||1906/07||2003/04||20|
|Canterbury Wizards (Canterbury)||1906/07||2016/17||19|
|Otago Volts (Otago/Southland)||1906/07||1987/88||13|
|Hawke's Bay (Hawke's Bay)||1914/15 - 1920/21||0|
|Central Districts Stags (Hawke's Bay/Taranaki/Manawatu/Nelson/Marlborough)||1950/51||2012/13||9|
|Northern Districts Knights (Northland/Bay of Plenty/Waikato/Gisborne)||1956/57||2011/12||8|
Points are awarded at the conclusion of each match during the season. With no final, the team with the most points is declared the champion. The points system for the 2011/12 season is as follows
- Won: 12 points
- Lost: 0 points
- Draw: 0 points
- Tie: 6 points
- One-innings match won (match that started with 10 hours or less playing time remaining): 6 points
- One-innings match tie: 3 points
- Abandoned (without a ball bowled) / No result (drawn one-innings match): 2 points
- Batting points: First Innings only up to 110 overs – first point at 250 runs, second point at 300 runs, third point at 350 runs, fourth point at 400 runs
- Bowling points: First Innings only up to 110 overs – first point at 3 wickets, second point at 5 wickets, third point at 7 wickets, fourth point at 9 wickets
The early winners of the competition during its "challenge match" period to 1921–22 were:
- 1906–07 – Canterbury
- 1907–08 – Auckland
- 1908–09 – Auckland
- 1909–10 – Auckland
- 1910–11 – Canterbury
- 1911–12 – Auckland
- 1912–13 – Canterbury
- 1913–14 – Canterbury
- 1914–15 – Canterbury
- 1915–18 – no competition due to World War I
- 1918–19 – Wellington (Dec 1918 to Jan 1919) and Canterbury (from Jan 1919)
- 1919–20 – Auckland
- 1920–21 – Wellington
|1940–45||(not contested due to World War II)|
|1991–92||Central Districts & Northern Districts|
|1998–99||Central Stags||Otago Volts|
|1999–00||Northern Knights||Auckland Aces|
|2000–01||Wellington Firebirds||Northern Knights|
|2001–02||Auckland Aces||Wellington Firebirds|
|2002–03||Auckland Aces||Wellington Firebirds|
|2003–04||Wellington Firebirds||Canterbury Wizards|
|2004–05||Auckland Aces||Wellington Firebirds|
|2005–06||Central Stags||Wellington Firebirds|
|2006–07||Northern Knights||Canterbury Wizards|
|2007–08||Canterbury Wizards||Wellington Firebirds|
|2008–09||Auckland Aces||Central Stags|
|2009–10||Northern Knights||Canterbury Wizards|
|2010–11||Canterbury Wizards||Otago Volts|
|2011-12||Northern Knights||Central Stags|
|2012-13||Central Stags||Otago Volts|
|2013-14||Canterbury Wizards||Otago Volts|
|2014-15||Canterbury Wizards||Auckland Aces|
- "Plunket Shield returns as premier domestic first-class trophy". New Zealand Cricket. Retrieved 20 June 2010.
- "Revision of Plunket Shield Matches". Evening Post. 84 (9): p. 2. 10 July 1912. Retrieved 22 March 2017.
- "New Zealand bring back Plunket Shield". Cricinfo.com. 4 November 2009.