Tuomas Haapanen was a Finnish violinist and music educator. He was born in Helsinki on 29 December 1924, the son of the conductor Toivo Haapanen. From early childhood, he attended rehearsals of the Finnish Radio Symphony Orchestra, which his father conducted.
Haapanen's first teacher was the violist Erik Karma, followed by the violinist Gösta Schatelowitz. While living in Pori with his father and the orchestra, he began studying with Erik Kronvall, who later became his professor at the Sibelius Academy; he also studied with Arno Granroth. After graduating from the Sibelius Academy in 1948, he continued his studies in Paris with Léon Nauwick and René Benedetti.
After returning to Finland, Haapanen played in the Helsinki Chamber Orchestra, formed by Paavo Berglund, from 1951 to 1961, while also performing with the Finnish Radio Symphony Orchestra from 1953 to 1962. In 1962 he left orchestral work and moved to Turku to become professor of violin at the newly established Turku Music Institute, now the Turku Conservatory. He taught there until 1978 and served as its rector from 1966 to 1978.
Haapanen then returned to Helsinki as professor of violin at the Sibelius Academy. Although he retired in 1990, he continued teaching at the academy until late in life. His pupils included Pekka Kuusisto, Jaakko Kuusisto, Petteri Iivonen, Elina Vähälä, Juha-Pekka Vikman, Laura Vikman, Réka Szilvay, Silja Nummi, and Dmitry Kogan.
He frequently served on juries for international violin competitions, including the International Henryk Wieniawski Violin Competition in 2001 and the Carl Nielsen International Violin Competition in 1992. He chaired the jury of the International Jean Sibelius Violin Competition from 1979 to 2000. Haapanen died in Helsinki on 8 January 2024, aged 99.