Graeme Bryce Segal FRS[2] (born 21 December 1941) is an Australian mathematician, and professor at the University of Oxford.

in 1967 from St Catherine's College, Oxford; his thesis, written under the supervision of Michael Atiyah, was titled Equivariant K-theory.

The Atiyah–Segal completion theorem in that subject was a major motivation for the Segal conjecture, which he formulated.

He has made many other contributions to homotopy theory in the past four decades, including an approach to infinite loop spaces.

He was also a pioneer of elliptic cohomology, which is related to his interest in topological quantum field theory.