Peter Ernest Ney, mathematician and probability theorist, died July 27, 2026, at his home in Madison, Wisconsin, of natural causes. 

He was 96. Born in Brno, Czechoslovakia on July 6, 1930, he immigrated to the United States in 1941 via Ireland and Brazil. He attended Riverdale Country School and the Massachusetts Institute of Technology and received his Ph.D. in mathematics from Columbia University in 1960. After a brief appointment at Cornell University, he joined the mathematics faculty of the University of Wisconsin–Madison, where he taught and conducted research until his retirement in 1996. His 1972 book,Branching Processes, co-authored with Krishna B. Athreya, became an important reference for generations of researchers in probability. He was a Guggenheim Fellow and a recipient of the Humboldt Research Award.His Erdős number was 1. Among his most prized possessions was a silver napkin ring given to him by an officer of the T.S.S. Almeda Star on his tenth birthday, during his family’s journey from Ireland to Brazil. The T.S.S. Almeda Star was sunk by a German U-boat in January 1941. At about that time, the Ney family was arriving in the United States from Brazil on the S.S. Argentina. 

He is survived by his sister, Hannah Sandson,his son, Paul Ney, and his daughter, Christine Lipp. 

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