Because it's handy thing to have, this is a list of the regions in New Zealand, and the major towns and cities in each one:
Northland (Whangarei, Kaikohe, Kaitaia)
Auckland (Auckland, Manukau, Waitakere, North Shore)
Waikato (Hamilton, Cambridge, Tokoroa, Huntly,Taupo, Morrinsville, Raglan, Te Awamutu)
Bay of Plenty (Tauranga, Rotorua, Thames, Paeroa, Whakatane )
East Coast (Gisborne, Wairoa)
Hawkes Bay (Napier, Hastings, Havelock North)
Taranaki (New Plymouth, Stratford, Waitara, Hawera)
Manawatu-Wanganui (Palmerston North, Wanganui, Fielding, Levin Dannevirke, Foxton )
Wellington (Wellington, Lower Hutt / Hutt City, Upper Hutt, Porirua, Otaki, Wairarapa, Masterton)
Marlborough (Picton, Blenheim,Kaikoura)
Tasman (Nelson, Richmond, Motueka)
West Coast (Westport, Greymouth, Hokitika)
Canterbury (Christchurch, Rangiora, Timaru)
Otago (Dunedin and Oamaru)
Southland (Invercargill)