Thepresentvolumewasdevotedto thethirdeditionofthe InternationalSym- sium on Algorithmic Game Theory (SAGT), an interdisciplinary scienti?c event intended to provide a forum for researchers as well as practitioners to exchange innovative ideas and to be aware of each other's e?orts and results. SAGT 2010 took place in Athens, on October 18-20, 2010. The present volume contains all contributed papers presented at SAGT 2010 together with the distinguished invited lectures of Amos Fiat (Tel-Aviv University, Israel), and Paul Goldberg (University of Liverpool, UK). The two invited papers are presented at the - ginning of the proceedings, while the regular papers follow in alphabetical order (by the authors' names). In response to the call for papers, the Program Committee (PC) received 61 submissions.Amongthesubmissionswerefour paperswith atleastonecoauthor that was also a PC member of SAGT 2010. For these PC-coauthored papers, anindependent subcommittee (EliasKoutsoupias,PaulG. Spirakis,andXiaotie Deng) made the judgment, and eventually two of these papers were proposedfor inclusion in the Scienti?c Program. For the remaining 57 (non-PC-coauthored) papers, the PC of SAGT 2010 conducted a thorough evaluation (at least 3, and on average 3.9 reviews per paper) and electronic discussion, and eventually selected 26 papers for inclusion in the Scienti?c Program. An additional tutorial, "Games Played in Physics", was also provided in SAGT 2010, courtesy of the academic research network Algogames (A??o?a????o) of the University of Patras.