This volume gathers the peer-reviewed proceedings of the Fifth France's International Conference on Complex Systems (FRCCS 2025), held in Bordeaux, France. FRCCS has become a key interdisciplinary venue for researchers and practitioners exploring the theory, modeling, and applications of complex systems. The book covers a broad range of topics, including network science, dynamical systems, data mining, machine learning, computational social science, and complex urban and biological systems. Contributions highlight both theoretical advances and innovative applications across scientific, industrial, and societal contexts. This collection will be a valuable reference for academics, engineers, and professionals working to understand, model, and manage complexity in real-world systems.