Advancement of Optical Methods and Fracture and Fatigue, Volume 3 of the Proceedings of the 2023 SEM Annual Conference & Exposition on Experimental and Applied Mechanics, the third volume of five 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 Experimental Mechanics, including papers in the following general technical research areas:Extreme EnvironmentsInterfacial FractureIntegration of Models & ExperimentsMechanics of Energy & Energetic MaterialsIntegration of Models & ExperimentsIn Situ Techniques for Fatigue & FractureMicroscale & Microstructural Effects on Mechanical BehaviorCharacterization Across Length ScalesExtreme Conditions & Environmental EffectsDamage, Fatigue and FractureStructure, Function and Performance