Shiing-Shen Chern (October 26, 1911 – December 3, 2004) was a Chinese-born American mathematician. He is regarded as a leader in geometry and one of the greatest mathematicians of the twentieth century. Chern's work extends over all the traditional fields of differential geometry. It includes areas currently fashionable (the Chern–Simons theory arising from a 1974 paper written jointly with Jim Simons), perennial (the Chern–Weil theory linking curvature invariants to characteristic classes from 1944, after the Allendoerfer–Weil paper of 1943 on the Gauss–Bonnet theorem), the foundational (Chern classes), and some areas such as projective differential geometry and webs that have a lower profile. He published results in integral geometry, value distribution theory of holomorphic functions, and minimal submanifolds. From 2000 to his death, Chern lived in Tianjin and taught at Nankai University. Chern died of heart failure in his home in Tianjin in 2004 at age 93.