This volume constitutes the refereed proceedings of the 19th International Symposium on Algorithmic Game Theory, SAGT 2026, held in Augsburg, Germany, during September 2026.

The total of 22 full papers and three 1- page Abstracts included in the proceedings was carefully reviewed and selected from 81 submissions. The SAGT conference series has become a leading interdisciplinary forum for the exchange of ideas and scientific progress acrosscontinents on incentives and computation arising in diverse areas, such as the oretical computer science, artificial intelligence, economics, operations research, and applied mathematics.