This book constitutes the refereed proceedings of the 41st IFIP International Conference on ICT Systems Security and Privacy Protection, SEC 2026, held in Perth, Australia, during June 9–11, 2026.The 39 full papers included in this book were carefully reviewed and selected from 164 submissions. They were organized in topical sections as follows: AI for Cyber Security; Cryptography; Cyber-Physical Systems Security; Data and Applications Security; Network and Systems Security; Privacy, Identification, Authentication and Access Control.