- Laura C. Gaardsted (Aarhus)
- Comp. number theory
- 1st Sep 2002 to 31st Dec 2002
- Steven Galbraith (Royal Holloway)
- Cryptograohy
- 12th Mar 2005 to 14th Mar 2005
- Shuhong Gao (Clemson)
- Commutative Algebra
- 21st Jul 2007 to 27th Jul 2007
- Joachim von zur Gathen (Paderborn)
- Computer Algebra
- 3rd Mar 1997 to 25th Apr 1997
- Pierrick Gaudry (École Polytechnique, Paris)
- Comp. number theory
- 6th Jan 2001 to 24th Mar 2001
- 1st Dec 2001 to 7th Dec 2001
- 7th Dec 2002 to 15th Dec 2002
- Katharina Geissler (TU Berlin)
- Comp. number theory
- 1st Oct 1999 to 30th Sep 2001
- Martine Girard (Leiden)
- Arithmetic Geometry
- 3rd Nov 2001 to 26th Nov 2001
- Stephen Glasby (Central Washington U)
- Group Theory
- 21st Jan 1997 to 31st Jan 1997
- David Glynn (Royal Society, NZ)
- Coding Theory, Finite Geometry
- 29th Jan 2002 to 28th Jan 2003
- 29th Mar 2005 to 25th Apr 2005
- Oliver Goodman (University of Melbourne)
- Topology
- 12th May 2005 to 13th May 2005
- Xavier Gourdon (École Polytechnique, Paris)
- Comp. number theory
- 1st Dec 1995 to 22nd Dec 1995
- Willem de Graaf (Trento)
- Lie Theory
- 30th Jul 1997 to 30th Aug 1997
- 1st Aug 2001 to 21st Aug 2001
- 1st Feb 2004 to 30th Sep 2004
- 5th Jun 2005 to 28th Jun 2005
- 9th Apr 2007 to 8th Jun 2007
- 3rd Apr 2011 to 21st Apr 2011
- Markus Grassl (Karlsruhe)
- Coding Theory, Quamtum Computing
- 8th Mar 2002 to 10th Apr 2002
- 14th Feb 2004 to 20th Mar 2004
- Matt Greenberg (Calgary)
- Arithmetic Geometry
- 21st Jul 2008 to 8th Aug 2008
- Jamie Gutierrez (Cantabria)
- Commutative Algebra
- 27th Oct 1998 to 3rd Nov 1998
