This book constitutes the refereed proceedings of the 14th International Symposium on Algorithmic Game Theory, SAGT 2021, held in Aarhus, Denmark in September 2021. The 26 full papers presented together with 4 abstract papers were carefully reviewed and selected from 73 submissions. In addition, the volume contains abstracts from 3 invited talks and 2 tutorial talks. The papers are organized in topical sections named: auctions and mechanism design, computational aspects of games, markets and matchings, and social choice and cooperative games.