This collection presents fundamentals and the current status of friction stir welding (FSW) and solid-state friction stir processing of materials and provides researchers and engineers with an opportunity to review the current status of the friction stir related processes and discuss the future possibilities. Contributions cover various aspects of friction stir welding and processing including their derivative technologies. Topics include, but are not limited to: • Derivative technologies • High-temperature applications • Industrial applications • Dissimilar alloys and/or materials • Lightweight alloys • Simulation • Characterization • Non-destructive examination techniques