This book constitutes the refereed proceedings of the 13th Annual European Symposium on Algorithms, ESA 2005, held in Palma de Mallorca, Spain, in September 2005 in the context of the combined conference ALGO 2005.The 75 revised full papers presented together with abstracts of 3 invited lectures were carefully reviewed and selected from 244 submissions. The papers address all current issues in algorithmics reaching from design and mathematical issues over real-world applications in various fields up to engineering and analysis of algorithms.