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.