Mechanics of Biological Systems and Materials and the Mechanics of Composite, Hybrid & Multifunctional Materials, Volume 3 of the Proceedings of the 2025 SEM Annual Conference & Exposition on Experimental and Applied Mechanics, the third volume of five from the Conference, brings together contributions to important areas of research and engineering. The collection presents early findings and case studies on a wide range of topics, including:Biomechanics of TissueHigh-rate Behavior of Biological and Biorelevant MaterialsMechanics and Morphogenesis of Multicellular SystemsCellular BiomechanicsMechanics of Functional BioarchitecturesNovel Techniques in Biomechanics and MechanobiologyRecycled Constituent CompositesDamage DetectionAdvanced Imaging of CompositesMultifunctional MaterialsComposite InterfacesTunable CompositesTime Dependent Materials