The European Congress of Mathematics, held every four years, is a well-established major international mathematical event. Following those in Paris (1992), Budapest (1996), Barcelona (2000), Stockholm (2004), Amsterdam (2008), Kraków (2012), and Berlin (2016), the Eighth European Congress of Mathematics (8ECM) took place in Portorož, Slovenia, June 20 – 26, 2021, with about 1700 participants from all over the world, mostly online due to the COVID pandemic.

Ten plenary and thirty invited lectures along with the special Abel and Hirzebruch lectures formed the core of the program. As in all the previous EMS congresses, ten outstanding young mathematicians received the EMS prizes in recognition of their research achievements. In addition, two more prizes were awarded: The Felix Klein Prize for a remarkable solution of an industrial problem and the Otto Neugebauer Prize for a highly original and influential piece of work in the history of mathematics. The program was complemented by five public lectures, several exhibitions, and 62 minisymposia with about 1000 contributions, spread over all areas of mathematics. A number of panel discussions and meetings were organized, covering a variety of issues ranging from the future of mathematical publishing and the role of the ERC to increase public awareness of mathematics.

These proceedings provide a permanent record of current mathematics of highest quality by presenting extended versions of seven plenary, six prize, and 14 invited lectures as well as 11 lectures from minisymposia keynote speakers, all of which were delivered during the Congress.