This book constitutes the proceedings of the 27th International Symposium on Stabilization, Safety, and Security of Distributed Systems, SSS 2025, held in Kathmandu, Nepal, during October 9-11, 2025.

The 21 full papers and 7 short papers together with 4 invited papers included in this book were carefully reviewed and selected from 59 submissions. The conference focuses on the design and development of distributed systems with a focus on systems that are able to provide guarantees on their correctness, performance, and/or security in the face of an adverse operational environment.