The Stratford–Okahukura Line (SOL) is a secondary railway line in the North Island of New Zealand, between the Marton - New Plymouth Line (MNPL) and the North Island Main Trunk (NIMT) Railway, with 15 intermediate stations. It is 144 km (89 mi) long through difficult country, with 24 tunnels, 91 bridges and a number of sections of 1 in 50 grade. Near Okahukura there is an unusual combined road-rail bridge over the Ongarue River, with the one-lane road carriageway below the single rail track. The line is not currently in service for rail traffic and is under a 30-year lease for a tourist venture. In July 2019 KiwiRail's CEO stated that reopening the line was a priority. Minister of Transport Michael Wood announced the government's 10-year plan for rail investment on 6 May 2021, which specifically stated that plans could include re-opening the Stratford to Okahukura line.

The Marton–New Plymouth line (MNPL) is a secondary railway in the North Island of New Zealand that links the Taranaki and Manawatū-Whanganui regions. It branches from the North Island Main Trunk railway (NIMT) at Marton and runs near the South Taranaki Bight of the west coast before turning inland, meeting the Stratford–Okahukura Line (SOL) at Stratford and running to New Plymouth. Construction of the line was completed in 1885, and along with the SOL it provided an alternate route to the NIMT with the SOL's completion in 1933 until the latter was mothballed in 2010. In its early days, the North Island's first regional express, the New Plymouth Express ran on the line, but it has been freight-only since the cancellation of passenger services on the line in 1977.