Harald Trefall (10 November 1925 – March 2008) was a Norwegian professor of experimental physics and later politician. He graduated from and worked at the University of Bergen, where he focused his work on cosmic radiation, and held a Ph.D. from the University of Oslo. His political career started as a Bergen city councillor for the Progress Party in 1983, until he left the party in 1986 and finished his term as an independent. He worked within various anti-immigration organisations in the late 1980s, and founded the Fatherland Party in 1990. He was a Hordaland county councillor for this new party from 1991 to 1995.
Trefall was born in Bergen on 10 November 1925. He graduated with a degree in mathematics and natural sciences at the University of Bergen in 1951, with an average of 1.21 or "exceptionally well". He became amanuensis at the same university in 1955, docent of physics in 1957, and was appointed professor of experimental physics from 1 April 1964. He obtained a Ph.D. from the University of Oslo in 1961 for six dissertations concerning topics within cosmic radiation. His initial academic area was cosmic radiation, but in 1962 he started researching X-ray phenomena brought forth by electron bombardment of the upper atmosphere in the zone of the polar aurora. He became internationally known for his balloon experiments at the Physics Institute at the University of Bergen, and initiated a cooperation with the Max Planck Institute of West Germany in the early 1960s. He retired as professor in 1995. Trefall died 82 years old in March 2008.