Topics in Modal Analysis, Testing & Parameter Identification I, Volume 9: Proceedings of the 43rd IMAC, A Conference and Exposition on Structural Dynamics, 2025, the ninth volume of twelve from the Conference brings together contributions to this important area of research and engineering.The collection presents early findings and case studies on fundamental and applied aspects of Modal Analysis, Modal Testing including papers on:Analytical MethodsModal ApplicationsBasics of Modal AnalysisExperimental TechniquesMulti Degree of Freedom TestingBoundary Conditions in Environmental TestingOperational Modal AnalysisNovel Techniques