Xavier Tolsa first studied engineering and later he turned to mathematics. After obtaining his PhD in mathematics in 1998 at the Universitat Autònoma de Barcelona (UAB), he spent about one year in the University of Göteborg – Chalmers and another year in the Université de Paris-Sud. Afterwards, he returned to the UAB as a Ramon y Cajal felow in 2001. Since 2003 he is ICREA Research Professor at the UAB. He has received several awards for his achievements, such as the Salem Prize (2002), the Prize of the European Mathematical Society (2004), the Prize Rei Jaume I (2019, first time awarded in the field of mathematics), Premio Nacional de Investigación Julio Rey Pastor (2024), or the Frontiers of Science Award (Beijing, 2024). He was invited lecturer at the European Congress of Mathematics in Stockholm (2004) and at the International Conference of Mathematicians in Madrid (2006). He has also been PI of two ERC Advanced Grants (2013-2018 and 2021-2026).

Xavier Tolsa works in mathematical analysis, and more specifically in harmonic analysis, geometric measure theory, and potential theory. More recently he has also become interested in elliptic PDE's and free boundary problems. Particularly, he is attracted by the relationship between analytic notions such as analytic capacity or harmonic measure, and geometric concepts like rectifiability. Around 2002 he proved that analytic capacity is semiadditive. This was an open problem since the early 1960s. Later on he studied related problems in higher dimensions. In particular, in a collaboration with F. Nazarov and A. Volberg he proved the so called David-Semmes conjecture in the codimension 1 case. This result has important applications to the study of harmonic measure and the Dirichlet problem for the Laplace equation, which are other main interests in his research. In geometric measure theory, one of his main contributions is the solution of Carleson's e² conjecture.