This book constitutes the refereed proceedings of the 11th International Symposium on Algorithmic Game Theory, SAGT 2018, held in Beijing, China, in September 2018.The 19 full papers presented together with 6 short papers and 5 plenary talks were carefully reviewed and selected from 54 submissions. The papers cover various important aspects of algorithmic game theory including market equilibrium, auctions and applications, two sided markets, cake-cutting, cooperative games, voting games, multi-agent scheduling, price of stability, various mechanism design problems: online-dynamics and multi-stages as well as revenue maximization and resource allocation and applications.