Fractured-porous and karst media constitute one of the most challenging geological systems to study due to their complex geometry patterns and hence associated scale-specific hydraulic and transport relevant properties. Because of their widespread distribution, such systems are of central importance for various research communities including hydrogeology and groundwater resources, geothermal systems, CO2 sequestration, nuclear waste repository site vulnerability, earthquake and volcano hazard assessment, and petroleum and mining engineering. They are subject to an extensive spectrum of methods for characterization and modeling of flow and transport dynamics, encompassing laboratory experiments, field studies, numerical simulations, and analytical techniques. The multiscale nature of fractured-porous and karst media poses significant challenges for coupling micro and macro scales, which is crucial for accurate representation and prediction of speleogenesis, reactive transport and the response to natural and anthropogenic boundary conditions. Addressing these challenges requires integrating approaches across different scales and leveraging advances in computational and analytical methods and deployment of state-of-the-art laboratory and field devices. We welcome contributions ranging from pore to field scales that focus on structural-geological characterization, characterization of flow and transport processes in the vadose and phreatic zone, as well as multiscale-coupling approaches. Topics of interest include, but are not limited to: (1) Advances in laboratory techniques, in-situ field methods, and analytical techniques for examining and understanding pore-scale to field-scale properties and behaviors; (2) Development and application of models to quantify and simulate complex flow and transport processes across multiple scales, enhancing predictive capabilities and practical; (3) Studies addressing water resource management, contamination remediation, environmental impact assessments, and the role of subsurface fracturing in earthquake and volcano hazard assessments; (4) Research aimed at improving the efficiency and safety of resource extraction in petroleum and mining engineering, as well as optimizing the exploitation of geothermal resources.