This book constitutes the refereed proceedings of the 8th International Symposium on Combinatorial Optimization, ISCO 2024, held in La Laguna, Tenerife, Spain, during May 22–24, 2024. The 30 full papers included in this book were carefully reviewed and selected from 46 submissions. They were organized in topical sections as follows: integer programming; graph theory; parameterized algorithms; approximation algorithms; integer programming for machine learning; and applications.