Dennis Gaitsgory (born 17 November 1973) is an Israeli-American mathematician.

He is a mathematician at Max Planck Institute for Mathematics (MPIM) at Bonn and is known for his research on the geometric Langlands program.

Born in Chișinău (now in Moldova) he grew up in Tajikistan, before studying at Tel Aviv University under Joseph Bernstein (1990–1996).

He received his doctorate in 1997 for a thesis entitled "Automorphic Sheaves and Eisenstein Series".

His work in geometric Langlands culminated in a joint 2002 paper with Edward Frenkel and Kari Vilonen,[1] establishing the conjecture for finite fields, and a separate 2004 paper,[2] generalizing the proof to include the field of complex numbers as well.