This open access book constitutes the proceedings of the 27th International Conference on Fundamental Approaches to Software Engineering, FASE 2024, held in conjunction with ETAPS 2024 which took place in Luxembourg in April 2024.  The 14 full papers included in this book were carefully reviewed and selected from 41 submission. The proceedings also include 5 short papers from the Test-Comp 2024 event that was hosted by FASE. They deal with the broad field of software engineering, focusing on requirements, design, architecture, modeling, applications of AI to software engineering and software engineering for AI-based systems, quality, model-driven engineering, processes, and software evolution.