Nils Olav Young Fearnley (14 December 1881 – 30 June 1961) was a Norwegian businessperson and landowner. He established several industries in Norway, among them Ranheim Papirfabrikk.
He was born in Kristiania to the ship-owner Thomas Fearnley (1841–1927) and his wife Elisabeth Young (1854–1932). He was a brother of Thomas Fearnley (1880–1961), grandson of painter Thomas Fearnley, paternal grandnephew of Carl Frederik Fearnley and maternal grandnephew of Nicolai Andresen.
In 1906 he married Ingeborg Heiberg, a daughter of Axel Heiberg. Their daughter Wanda was married to Dag Klaveness.
N. O. Young Fearnley went to a trade school in Leipzig, Germany. He also spent learning years at the Young properties in Hakadal and a timber trading company in London. In 1906 he founded Meraker Brug, where he was the factory manager until 1912. He then worked as the manager of Union Co until 1919. He established several other industries in Norway, among them Ranheim Papirfabrikk. After 1919 he was a landowner based at Aas in Hakadal.
Fearnley chaired Papirindustriens arbeidsgiverforening, the Norwegian Museum of Cultural History and the Norwegian Kennel Club and was a vice president of the Federation of Norwegian Industries. He chaired the supervisory council of Ringnes Bryggeri, was a board member of the Norwegian Employers' Confederation, Forsikringsselskapet Viking, Lillestrøms Cellulosefabrikk as well as Meraker Brug and Ranheim Papirfabrikk. He was a founder and honorary member of the gentlemen's club SK Fram.