This first of three volumes presents papers from the fourth series of the NODYCON conferences, held at Stevens Institute of Technology, Hoboken, NJ, USA, in June of 2025. The conference papers reflect a broad coverage of traditional topics in nonlinear dynamics, as well as newly established and emerging strands of research. These include:Data-Driven Nonlinear Dynamics and Machine Learning ApplicationsMetamaterials, Structural Health Monitoring, and Adaptive Vibration ControlAI-Driven Modeling for Engineering and Complex SystemsComputational and Experimental Mechanics of Nonlinear SystemsNonlinear Energy Harvesting Techniques and Vibration ControlReduced-Order Models and Advanced Analytical Methods in Nonlinear DynamicsFluid-Structure Interaction and Multiphysics Nonlinear DynamicsNonsmooth Dynamics, Impacts, and Bifurcations in Engineering SystemsRotordynamics, Magnetic Bearings, and High-Speed Machinery DesignComputational Intelligence and Experimental Validation in Nonlinear Dynamics