This book presents select proceedings of the sixth National Conference on Reliability and Safety (NCRS 2025), Reliability and Safety Assessment for Safety Critical Systems. The topics covered include the assessment of safety and security of complex technological systems ranging from spacecrafts, nuclear power plants to medical facilities dealing with nuclear materials. The title deals with studies related to improving system, and human reliability studies.  There is also incorporation of emerging techniques like artificial intelligence, and machine learning for detection and assessment of threats and vulnerabilities in financial and complex technological systems. The book will be a valuable reference for beginners, researchers, and professionals interested in risk and reliability studies and for development of sustainable solutions for the society.