The Ōhikanui River is a tributary of the Buller River in New Zealand's South Island. It flows north for , joining the Buller from its outflow into the Tasman Sea. It and its smaller neighbour the Ohikaiti River are often called the Big Ohika River and Little Ohika River respectively. Another variation is Ohika-nui. Ōhikanui River has been the official name since 21 June 2019. The New Zealand Ministry for Culture and Heritage gives a translation of "place of large incantations" for Ōhikanui. A surveyor named the tributaries to the west of the Ōhikanui River using Greek letters, as Alpha, Beta, Gamma, Delta and Eta Creeks. He also named Dumpling Creek after he returned to camp on a cold wet day and was given a dumpling stew. The Ōhikanui River is a tributary consisting of a bouldery river bed and clear swift water. It flows through the paparoa wilderness area which is unaltered (with no tracks or huts), though Buckland Peak Hut is just outside the catchment. The area is popular with trampers because of its natural environment, with Brown trout fishers, who use the river about 140 times a year, and with deer stalkers. Most of the valley runs over a Late Devonian pluton of leucocratic muscovite granite. The mountains at the southern end of the valley, made of early Paleozoic Pecksniff Metasedimentary Gneiss, have been carved by glaciation to form cirques and sharp ridges. The valley has high glacial aggradation, and lower degradation, terraces. Forest covers the whole valley, with no grassy flats. Tall forest is replaced by stunted forest, merging to alpine scrub, at to , depending on aspect, landform and cold air drainage. The valley has an average of over of rain, more than 200 wet days a year and rainfall has been measured at over per hour. In the 1970s red deer, goats and rats were scarce, possums in moderate numbers and stoats everywhere. The valley now has pest control as part of the Paparoa Range TB Management Area. The lower valley has cabbage tree, northern rata, rimu, kahikatea, kamahi, kanono, karamu, kareao, kiekie, kōwhai, māhoe, mataī, porokaiwhiri, toro, tutu, yellow silver pine, mountain toatoa and mountain beech. The middle valley has horopito, silver beech, tawhai raunui, mountain tōtara and rimu, with crown fern and bush rice grass (Microlaena avenacea) in the understorey. Silver and mountain beech dominate the upper slopes, with Archeria traversii and