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 Environments Interfacial Fracture Integration of Models & Experiments Mechanics of Energy & Energetic Materials Integration of Models & Experiments In Situ Techniques for Fatigue & Fracture Microscale & Microstructural Effects on Mechanical Behavior Characterization Across Length Scales Extreme Conditions & Environmental Effects Damage, Fatigue and Fracture Structure, Function and Performance