This book offers a timely reference on signal processing methods, and their application to the field of machine diagnostics and condition monitoring. Gathering selected contributions to the 3rd International Workshop on Signal Processing Applied to Rotating Machinery Diagnostics, SIGPROMD2025, held on November 9–11, 2025, in Setif, Algeria, it discusses vibration and acoustics in mechanical systems and structures, condition monitoring in non-stationary operations, and artificial intelligence applied to machinery fault diagnosis. It also reports on advanced modeling techniques in machinery, and reliability and lifecycle management strategies. All in all, this book offers extensive information for researchers, engineers, and professionals in the fields of mechanical engineering, signal processing and diagnostics, and a good balance of theoretical models and best practices.