Model Validation and Uncertainty Quantification, Volume 3: Proceedings of the 43rd IMAC, A Conference and Exposition on Structural Dynamics, 2025, the third 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 Model Validation and Uncertainty Quantification, including papers on:Model Form Uncertainty: Round Robin Challenge UQVI (Uncertainty Quantification in Vibration Isolation)Uncertainty Quantification in Sensing SystemsBayesian and Other Methods for Structural Health MonitoringSurrogate ModelingUncertainty Quantification in Digital Twin and Data-Driven ModelsUncertainty Quantification and Propagation in Structural Dynamics