This book collects a part of the contributions presented at the 9th Italian National Conference of the Researchers of Geotechnical Engineering (CNRIG 2026) focused on Prediction and Performance in Geotechnical Engineering. The conference was held on July 1–3, 2026, at the University of L’Aquila, Italy, and it was promoted by the National Group of Geotechnical Engineering (GNIG). The conference addressed the crucial issue of the comparison between predictive models and real behavior of geotechnical structures and systems, encompassing theory, practice, and innovation. The proceedings cover a wide range of classical and emerging topics in geotechnical engineering, including soil characterization and advanced numerical modeling, performance-based and observational approaches, management of uncertainties in geotechnical design, integration between predictive models and monitoring, safety and sustainability of geotechnical structures and systems in different risk scenarios, innovative monitoring techniques, digital solutions, and emerging technologies. This book includes the keynote contributions and the conference papers related to the themes Characterization and modeling of soils and rocks and Geotechnical structures and systems.