New Zealand's first railway opened in 1863 between central Christchurch and a temporary port at Ferrymead; the full line opened to Lyttelton in 1867 with the completion of the Lyttelton Rail Tunnel. Over the next 100 years, the rail network expanded to cover the country, however progress was slow due to difficult terrain. The line between Auckland and Wellington was completed in 1908 when railheads met between National Park Village and Ohakune, and the line between Christchurch and Greymouth was completed in 1923 with the opening of the 8.55 km (5.31 mi) Otira Tunnel under the Southern Alps main divide. Two world wars, the Great Depression and difficult terrain meant it took until 1945 for the line between Christchurch and Picton to be completed. The final link in the rail network came in 1962 with the commencement of roll-on-roll-off rail ferry services between Wellington and Picton. The first mainline diesel locomotives were introduced into service in 1954, with the last steam locomotives withdrawn from revenue service in October 1971.

Many rural branch lines closed in the latter half of the 20th century due to competition from road transport. Passenger services were cut back as car ownership rose and air travel became more affordable, although several services were retained and re-branded as tourist services. Auckland's suburban rail network was nearly scrapped in the late 1980s due to low passenger numbers. Wellington's suburban network experienced a decline, but passenger numbers remained strong. This was due to the city's geography being ideal for rail transport and the fact the network was electrified (completed 1938-40 and 1953-55).

In 1993, the government under Prime Minister Jim Bolger privatised the whole rail network. Privatisation was soon deemed an abject failure and it brought worsening quality of service and state of infrastructure, swinging the political consensus in favour of renationalisation. In 2004, the government under Prime Minister Helen Clark bought back the rail infrastructure assets and later in 2008, bought back the remainder to form the present day KiwiRail.

In 2003, the rail renaissance in Auckland began with the opening of a new underground central terminus, Britomart. In 2014-15 the Auckland network was electrified and for the first time, total passenger boardings exceeded those of Wellington. The renaissance has caused demand to outstrip the capacity of Britomart station, and in 2016, works started on a new rail tunnel through central Auckland to turn Britomart into a through station.

On both the North and South islands, long distance passenger rail service is provided by state-owned KiwiRail under the brand Great Journeys New Zealand. New Zealand has three main passenger lines.

The Northern Explorer provides service three times per week from Auckland to Wellington and back. The Coastal Pacific provides service on the South Island from Christchurch to Picton and back, timed to meet the Interislander ferry service between Wellington and Picton.

The TranzAlpine, one of the most popular routes, provides service between Christchurch and Greymouth, including a stop inside the Arthur's Pass National Park. Passengers may pay extra to upgrade to Scenic Plus, in which meals made using local produce are included.

KiwiRail also operates a weekday commuter service known as the Capital Connection between Palmerston North and Wellington (departing Palmerston North in the morning and returning in the evening).

There is also the Wairarapa Connection between Masterton and Wellington, which operates five services in each direction on weekdays and two services in each direction on weekends. Operated by Wellington commuter operator Metlink, this train blurs the line between long distance and commuter rail - it operates a commuter-orientated timetable and doesn't have the snack servery, open air carriages, checked luggage or reserved seats of long distance services; but it has the luggage room, long-distance seats, tray tables, power outlets and toilets which commuter services in New Zealand don't have.

Station stops for all lines, with links to relevant city articles, are as follows:

Northern Explorer takes you in one day the 681 km (423 mi) length of the North Island Main Trunk between Auckland and Wellington. Construction of the line begun in 1885 and only completed in 1908, including marvels of Victorian engineering such as the Raurimu Spiral, Turangarere Horseshoe and Makatote Viaduct. As ever in New Zealand, this exhilarating journey traverses ever-changing scenery; from rocky coast to volcanoes through uplands, passing lush green pasture lands and thick native bush.
Auckland Strand - Papakura in South Auckland - Hamilton - Otorohanga (for Waitomo Caves) - National Park - Ohakune - Palmerston North - Paraparaumu - Wellington

The Coastal Pacific is a 5.5-hour 348 km (216 mi) journey along the Main North Line between Christchurch and Picton, connecting with Cook Strait ferries to Wellington. The line only opened to through traffic in December 1945, having been delayed by difficult terrain each side of Kaikoura, plus two World Wars and the Great Depression. The line was damaged in the 14 November 2016 Kaikoura earthquake and the Coastal Pacific service in December 2018 is running a little slower than normal. Picton - Blenheim - Seddon - Kaikoura - Mina (for Cheviot) - Waipara - Rangiora - Christchurch

The TranzAlpine is a 4.5-hour 223 km (139 mi) journey along the Midland Line between Christchurch and Greymouth. The train travels across the Canterbury Plains and up the Waimakariri Gorge into the Southern Alps, before tunneling underneath the main divide and travelling down river valleys to the West Coast. The Otira Tunnel (1923) under the main divide is 8.5 km long, with the Arthur's Pass end 250 m higher than the Otira end: some trains require five diesel locomotives to haul them up the tunnel, which explains why they close the viewing platforms.
Christchurch - Rolleston - Darfield - Springfield - Cass - Arthur's Pass National Park - Otira - Jacksons - Moana - Kokiri - Brunner - Greymouth

Capital Connection (Commuter Service - one return service on weekdays only) Palmerston North - Shannon - Levin - Otaki - Waikanae - Paraparaumu - Wellington

Te Huia (Commuter Service - two return services on M-W, Sa and three on Th-F) Auckland Strand - Puhinui - Papakura - Huntly - Rotokauri - Hamilton. This follows the route of the Northern Explorer between Auckland and Hamilton, taking 2 hours 40 minutes. The train has a cafe, useful for breakfast on the 6AM departure from Hamilton. There are connections to the Auckland rail network at Puhinui and Papakura, which may be convenient to use Britomart on Queen Street, rather than the more isolated Strand station. There is a significant discount for using a Bee card to buy your ticket, so use this rather than cash if you are going more than a single stop.

Wellington, despite being smaller than Auckland, has the larger (in route kilometers) and the more patronised (in trips per capita) suburban system. The trains are part of the Metlink network and are operated by Transdev. There are five lines serving Greater Wellington as far north as Waikanae and Masterton. Electric multiple unit trains operate all services except the Wairarapa Line service (also known as the Wairarapa Connection) between Masterton and Wellington, which uses diesel-hauled carriage trains due to the lack of electrified track beyond Upper Hutt.

Services typically operate half-hourly seven days a week on the Johnsonville, Kapiti, and Hutt Valley Lines. Melling Line services typically operate hourly on weekdays; the line does not operate on weekends. Services are more frequent at peak times. The Wairarapa line operates five-times daily (three peak, two off-peak) each way on weekdays and twice daily each way on weekends.

Single-trip tickets can be purchased with cash from the train manager on board. Ten-trip tickets and monthly passes for regular trips between two stations can be purchased at ticket offices at major stations and some retail outlets across the region. Day explorer and bus-train combined passes are also available.

Bicycles can be carried free on off-peak services on a first-come-first-served basis. Most peak services will not take bicycles in the peak direction (to Wellington in the morning, from Wellington in the evening).

After facing near closure in the late 1980s, Auckland's suburban network had a major turning point in 2003 when the new Britomart central terminus opened. As a result of extensive track works and electrification in 2014-15, Auckland's network has overtaken Wellington's network in passenger numbers.

There are four lines, stretching west to Swanson and south to Onehunga, Manukau and Papakura. Weekday off-peak services typically operate every 20 to 30 minutes. An hourly diesel shuttle service connects Pukekohe with electric trains at Papakura. An underground city centre extension, the City Rail Link, is under construction and is expected to open in 2025.

There are some shorter sections of railway which are more suited to a day out than as a regular form of passenger transport. These often operate preserved steam or diesel locomotives and carriage stock.

• 001 Dunedin Railways, ☏ +64 3 477-4449. Based out of the historic Dunedin Railway Station, it runs tourist trains northward along the coast to Oamaru, and inland towards Hindon via the spectacular Taieri River Gorge. The Taieri River Gorge route once extended all the way to Pukerangi and Middlemarch, but these services have been cancelled due to COVID.  
• -37.2083174.78562 Glenbrook Vintage Railway, Onehunga, South Auckland. Runs on many summer Sundays and some occasional other days. 7-km steam railway. (updated Dec 2017)