| Last Name Sort descending | First Name | Year | City | Section/Speaker Type |
|---|---|---|---|---|
| Orlov | D. | 2002 | Beijing | Algebra |
| Ornstein | Donald S. | 1970 | Nice | Analysis |
| Orszag | S. A. | 1986 | Berkeley | Numerical Methods & Computing |
| Oseen | C. W. | 1936 | Oslo | Plenary |
| Osher | Stanley | 1994 | Zurich | Numerical Analysis & Scientific Computing |
| Osher | Stanley | 2010 | Hyderabad | Plenary |
| Oshima | T. | 1983 | Warszawa | Lie groups & representations |
| Osin | Denis | 2018 | Rio de Janeiro | Geometry |
| Osinga | Hinke | 2014 | Seoul | Mathematics in Science and Technology |
| Osserman | R. | 1978 | Helsinki | Geometry |
| Oster | George | 1994 | Zurich | Applications of Mathematics in the Sciences |
| Osterwalder | K. | 1983 | Warszawa | Mathematical physics & mechanics |
| Osterwalder | Konrad | 2006 | Madrid | Mathematics Education and Popularization of Mathematics |
| Osthus | Deryk | 2014 | Seoul | Combinatorics |
| Ostrik | Victor | 2014 | Seoul | Lie Theory and Generalizations |
| Ostrover | Yaron | 2014 | Seoul | Geometry, Dynamical Systems and Ordinary Differential Equations |
| Ostrowski | O. | 1928 | Bologna | Analysis |
| Otto | Felix | 2002 | Beijing | Application of Mathematics in the Sciences |
| Ozawa | Narutaka | 2006 | Madrid | Operator Algebras and Functional Analysis |
| Ozdaglar | Asu | 2022 | Virtual | Control Theory and Optimization |
| Ozsváth | Peter | 2006 | Madrid | Topology |
| Paatero | V. | 1936 | Oslo | Analysis |
| Pacard | Frank | 2010 | Hyderabad | Geometry |
| Pach | János | 2014 | Seoul | Combinatorics |
| Padé | H. | 1900 | Paris | Analysis |