The 111th Peripatetic Seminar on Sheaves and Logic (PSSL 111) took place on Sep 4th and Sep 5th 2025 in Bologna, Italy.

Note that the dates were not on a weekend, but on a Thursday and Friday, unlike the usual PSSL tradition.

PSSL is a long-running series of informal gatherings covering all aspects of category theory and its applications, typically held over a weekend at a university in Europe. The first PSSL was held in Oxford, in May 1976. This is the 111th PSSL, following meetings in Tallinn, Leiden, Terrasini, and Athens.

Local organizers