The ECCO XXXIX - CO 2026 joint conference will take place in Lisboa, Portugal, aiming to bring together researchers in the field of Combinatorial Optimization to present their work, share experiences, and discuss recent advances in theory and applications. The primary objectives are:

• exchanging results and experiences in solving real-world combinatorial optimization problems
• reporting on development and implementation of appropriate models and efficient solution methods for combinatorial optimization problems
• establishing networking contacts between individuals and research groups working on related topics
• promoting the work on combinatorial optimization (theory and applications) to the broader scientific community
• identifying challenging research problems for the field, as well as promising research outlets (both in theory and applications)
• promoting interactions with researchers in other related fields

ECCO (European Chapter on Combinatorial Optimization) is a Working Group of EURO (Association of European Operational Research Societies) that provides an excellent opportunity to discuss recent and important issues in Combinatorial Optimization and its applications. CO series of biennial symposia, The Combinatorial Optimization Conferences, started in the UK in 1977 with meeting venues alternated between the UK and continental Europe.

A special issue of the Journal of Combinatorial Optimization will be devoted to work presented at the conference. All articles will be refereed according to the high standards of the journal. Details of the process will be given during the conference.