The 12th edition of the Winter School will take place at the Hotel Londres (https://www.hotelondres.com/en/) , Estoril, from the 19th to the 23rd of January 2026. In the spirit of the previous editions, the main objective of the school is to provide an opportunity for PhD students to get together and attend high level courses in the field of Network Optimization. In this edition of the school, the lecturers and subjects to be addressed are: William Cook - The Traveling Salesman Problem and Computational Discrete Optimization Martine Labbé - (Bi)Linear Bilevel Optimization Problems: models, algorithms and applications Ivana Ljubic - Network Resilience and Vulnerability: Protecting the Critical Infrastructure Giovani Rinaldi - QUBO: exact, heuristic, and quantum methods. Hande Yaman - Covering problems and length bounded connectivity The school is part of the activities of the ENOG (European Network Optimization Group). Potential participants are invited to submit their CVs to the address netopt2026@fc.ul.pt no later than October 15. Further information is available in the webpage (https://netopt2026.campus.ciencias.ulisboa.pt).