This book constitutes the proceedings of the 11th IFIP WG 2.2 International Conference on Fundamentals of Software Engineering, FSEN 2025, held in Västerås, Sweden during April 7–8, 2025. The 11 full papers and 1 short paper included in this book were carefully reviewed and selected from 30 submissions. They deal with all aspects of formal methods, with a strong emphasis on promoting their industrial applications and integrating them with practical engineering practices.