Champaign—Philippe Tondeur, University of Illinois Professor Emeritus of Mathematics, died October 15, 2026, in Champaign.

Philippe Tondeur was born Dec 7, 1932, in Zurich, Switzerland.

He was one of the five children of Jean Matthieu and Simone (Lapaire) Tondeur. His father died during his school years, and Philippe’s professional life started as a teenager on a factory floor.

After several years of day job and night school he earned a degree in Engineering for his night studies, and a few years later a Ph D degree in Mathematics from the University of Zurich. With this turn to mathematics a light had turned on in his life, and these degrees gave him wings. He became a Research Fellow and Lecturer at the University of Paris, at Harvard University, the University of California at Berkeley, an Associate Professor at Wesleyan University, before joining the UIUC faculty in 1968, where he became a Full Professor in 1970.

Philippe has been a Visiting Professor at the Universities of Buenos Aires, Auckland, Heidelberg, Rome, Santiago de Compostela, Leuven, as well as at the Eidgenoessische Technische Hochschule in Zurich, the Ecole Polytechnique in Paris, the Max Planck Institute for Mathematics in Bonn, Keio University in Tokyo, Tohoku University in Sendai, and Hokkaido University in Sapporo.

His research and educational interests evolved over time. His preferred mathematical topics were Topology and Differential Geometry, enthusiastically pursued during his entire career. But his interests ranged widely in the Mathematical Sciences and Mathematical Physics. In later years, his interests included the role of mathematics in science and society; innovation policy; institutional governance; and leadership development. In 2008 he was elected a Fellow of the Society for Industrial and Applied Mathematics. In 2009 he was elected Fellow of the American Association for the Advancement of Science. In 2012 he was chosen a Fellow in the Inaugural class of Fellows of the American Mathematical Society.

He served for several decades as a faculty member at UIUC, totally absorbed by research and teaching mathematics. His aim was to perform in the chosen field to the best of his abilities, and simultaneously participate in the governance of the department and university. To be part of such a community of colleagues, all gifted and passionately devoted to their discipline, and the spreading of their accumulated knowledge to the next generations, is an immense gift, and the basis for a happy life. He was honored to serve as department chair for mathematics for a number of years. This position offered opportunities at a different level. Successes were achieved in collaboration with fantastic colleagues, with a similar devotion to a life in mathematics research, teaching and public service. For the last few years of his career he was fortunate enough to be asked by the National Science Foundation to serve as Director of its Division of Mathematical Sciences. This designation includes mathematics, statistics, and computational mathematics. He felt privileged to be able to successfully apply his lifelong professional and leadership experiences to advance the mathematical sciences at the national level in his adopted country.

He retired in 2002 from this position. During his retirement Philippe Tondeur served on and chaired numerous Governing and Advisory Boards in the Mathematical Societies. He also served as a member of the National Committee on Mathematics of the U.S. National Research Council, and as a US Delegate to the General Assembly and International Congress of Mathematician in Madrid. He served on the Science Policy Committee and other Committees of the Mathematical Association of America and of the American Mathematical Society, as well as the Joint Policy Board of the Mathematical Sciences in the US. He particularly enjoyed the decade long service on the Committee on Science Policy of the Society for Industrial and Applied Mathematics.

Philippe is survived by his wife Claire, his cherished and joyous companion for over 60 years of bliss, and his sister Thérèse, as well as ten nieces and nephews, living in the UK, Switzerland, France, Morocco and Dubai.