Spencer Janney Bloch (born May 22, 1944; New York City[1]) is an American mathematician known for his contributions to algebraic geometry and algebraic K-theory.

Bloch is a R. M. Hutchins Distinguished Service Professor Emeritus in the Department of Mathematics of the University of Chicago.

[4] Bloch and Kazuya Kato formulated the motivic Bloch–Kato conjecture relating Milnor K-theory and Galois cohomology in 1986[5] and the Bloch–Kato conjectures for special values of L-functions in 1990.

[6] Bloch is a member of the U.S. National Academy of Sciences[7] and a Fellow of the American Academy of Arts and Sciences[8][9] and of the American Mathematical Society.

[11] He also received a 2021 Leroy P. Steele Prize for Lifetime Achievement.