Matthias Flach is a German mathematician, professor and former executive officer for mathematics (department chair) at California Institute of Technology.

Research interests includes:
Arithmetic algebraic geometry (see Glossary of arithmetic and Diophantine geometry).Special values of L-functions.Conjectures of:BlochBeilinsonDeligneBloch–Kato conjecture (see also List of conjectures).Galois module theory.Motivic cohomology.Ph.D. University of Cambridge UK 1991 Dissertation: Selmer groups for the Symmetric Square of an Elliptic Curve – Algebraic geometry B.A., J.W. Goethe Universität, Frankfurt, Germany, 1986Iwasawa Theory and Motivic L-functions (2009) – Flach, MatthiasOn Galois structure invariants associated to Tate motives – Matthias Flach and D. Burns, King's College London On the Equivariant Tamagawa Number Conjecture for Tate Motives, Part II. (2006) – Burns, David; Flach, Matthias.Euler characteristics in relative K-groups – Matthias FlachThe equivariant Tamagawa number conjecture: A survey (with an appendix by C. Greither) – Matthias FlachA geometric example of non-abelian Iwasawa theory, June 2004, Canadian Number Theory Association VIII Meeting – Flach, Matthias.The Tamagawa number conjecture of adjoint motives of modular forms (2004) – Diamond, Fred; Flach, Matthias; Guo, Li.Adjoint motives of modular forms and the Tamagawa number conjecture (2001) – Fred Diamond; Matthias Flach; Li Guo.