| Last Name | First Name | Year | City Sort ascending | Section/Speaker Type |
|---|---|---|---|---|
| Oh | Yong-Geun | 2006 | Madrid | Geometry |
| Okounkov | Andrei | 2006 | Madrid | Probability and Statistics/Prize winner |
| Ono | Kaoru | 2006 | Madrid | Topology |
| Opdam | E.M. | 2006 | Madrid | Lie Groups and Lie Algebras |
| Osterwalder | Konrad | 2006 | Madrid | Mathematics Education and Popularization of Mathematics |
| Ozawa | Narutaka | 2006 | Madrid | Operator Algebras and Functional Analysis |
| Ozsváth | Peter | 2006 | Madrid | Topology |
| Picard | Dominique | 2006 | Madrid | Probability and Statistics |
| Popa | Sorin | 2006 | Madrid | Plenary |
| Pulvirenti | Mario | 2006 | Madrid | Partial Differential Equations |
| Quarteroni | Alfio | 2006 | Madrid | Plenary |
| Ralston | Anthony | 2006 | Madrid | Mathematics Education and Popularization of Mathematics |
| Rathjen | Michael | 2006 | Madrid | Logic and Foundations |
| Reingold | Omer | 2006 | Madrid | Mathematical Aspects of Computer Science |
| Rodnianski | Igor | 2006 | Madrid | Mathematical Physics |
| Rordam | Mikael | 2006 | Madrid | Operator Algebras and Functional Analysis |
| Ros | Antonio | 2006 | Madrid | Geometry |
| Rothschild | Linda | 2006 | Madrid | Analysis |
| Roughgarden | Tim | 2006 | Madrid | Mathematical Aspects of Computer Science |
| Rouquier | Raphael | 2006 | Madrid | Algebra |
| Rubinfeld | Ronitt | 2006 | Madrid | Mathematical Aspects of Computer Science |
| Ruzsa | Imre | 2006 | Madrid | Combinatorics |
| Santos | Francisco | 2006 | Madrid | Combinatorics |
| Sapir | Mark | 2006 | Madrid | Algebra |
| Savin | Ovidiu | 2006 | Madrid | Partial Differential Equations |