Tsuneo Tamagawa, Andrew W. Phillips Professor of Mathematics Emeritus at Yale University, passed away peacefully in New Haven, CT on the morning of December 30, 2017 at the age of 92. He was the husband of the late Kimiko Kozu Tamagawa. Born in Tokyo, Japan in 1925, the son of Hisao and Miyo Tamagawa, Professor Tamagawa received his Ph.D. from Tokyo University in 1954 and taught there from 1950 to 1962. In the United States he was a member of the Institute for Advanced Study at Princeton, New Jersey and held faculty positions at Johns Hopkins University and Northwestern University. He joined the Yale University faculty in 1963 and was appointed to the Phillips Professorship in 1976. He was widely known in the mathematics field for his fundamental contributions to research on the arithmetic aspects of classical groups, which involve mathematical theories having their roots in geometry. Perhaps his most celebrated achievement is his synthesis of the so-called Tamagawa Number, which has opened new areas of thought in a field that has been worked over heavily by number theorists for generations. His articles on mathematical theory have been published in journals in both Japan and the United States. He is survived by sisters Kazuko Kobayashi, Nobuko Shimada, and brother Shinji Tamagawa of Tokyo, Japan; children Kiyoshi of Austin, TX, Takashi of North Haven, CT, Satoshi of Kawasaki, Japan, Sahoko, of Berkeley, CA, and Emiko of Attleboro, MA; and grandchildren Hisayuki and Rieko Tamagawa of Kawasaki and Mira and Leo Gordon of Berkeley. He was predeceased by brothers Hajime Tamagawa and Tetsuo Tamagawa. The family wishes to thank the staff members at the Whitney Center and Yale-New Haven Hospital for their excellent care of Prof. Tamagawa. In lieu of flowers they request that contributions be made to the Audubon Society in his honor, at www.audubon.org. A memorial in his honor will take place on Saturday, March 31 at 3 p.m. at the Cultural Activities Center at the Whitney Center, 200 Leeder Hill Dr., Hamden, CT. Family members, colleagues and friends of Professor Tamagawa will offer musical performances and speak about his personal and professional life. A reception will follow immediately in the CAC. Please contact Kiyoshi Tamagawa at tamagawk@southwestern.edu for more information.