István Fenyő (5 March 1917 – 28 July 1987) was a Hungarian mathematician, whose first name was also known as "Étienne, Stefan, Stephan or Stephen". He was best known for his publications of applied mathematics. He made significant contributions to analysis, algebra, geometry, integral equations and many other fields that pertain to his interests. Life and education István Fenyő was born on 5 March 1917 in Budapest, Austria-Hungary into a family who were "cultured and interested in arts". He attended Pázmány Péter Catholic University in Budapest to study mathematics and physics; his advisor was Lipót Fejér who was the chair of mathematics "for 48 years from 1911 to 1959". After his graduation in 1939, which allowed him to teach those subjects at secondary school in Hungary, he continued his studies in chemistry and in 1942 earned the diploma. He then worked on his research publication "Über die 'Polynom-Kerne' der linearen Integralgleichungen" in 1943. During his doctorate, he developed his thesis "On the theory of mean values" (translated) in 1945. Career After Fenyő's education, he held his position as the lecturer at the Technical University of Budapest. In 1950, he was promoted to Extraordinary Professor of Mathematics. A decade later, he became the full Professor and then the first chair of mathematics and computer sciences. In 1968, he "left the Technical University of Budapest" and became the visiting professor in Germany "for several years". He was the first head of department until 1982. Personality Based on Paganoni, Fenyő became fascinated and interested in sciences, humanities and arts since he was a child: Fenyő was a passionate mathematician who readily engaged in conversation and showed a great affinity to work on his publications. He was able to speak in different languages; Paganoni describes his warm personality: Mathematical Work Similar to Paul Erdős and Leonardo da Vinci, Fenyő was a prolific and brilliant publisher of mathematical work; during the late 1940s, he wrote numerous works; some in collaboration with mathematicians, like János Aczél, while he published others by himself. His two works, "Mathematics and the dialectial materialism" and "Les fondaments des mathématiques et la philosophie du matérialisme dialectique" were "delivered at the Tenth International Congress of Philosophy in Amsterdam" and "printed in the Proceedings" in 1949. His two-volume work, "Mathematics in electrical engineering", was published in 1964, and a decade later a Bulgarian translation of these volumes was published in 1977 and 1979.