This book constitutes the refereed proceedings of the 13th International Conference on Principles of Distributed Systems, OPODIS 2009, held in Nimes, France, in December 2009. The 23 full papers and 4 short papers presented were carefully reviewed and selected from 72 submissions. The papers are organized in topical sections on distributed scheduling, distributed robotics, fault and failure detection, wireless and social networks, synchronization, storage systems, distributed agreement, and distributed algorithms.