In a rapidly evolving world, technological innovation continues to shape economic growth, sustainability, and societal development. The book New Technologies, Development and Application IX – Volume 3 presents selected peer-reviewed papers from the 12th International Conference on New Technologies, Development and Application (NT-2026), held from 25 to 27 June 2026. This volume provides a multidisciplinary overview of current research and practical applications in advanced and emerging technologies. It highlights recent achievements in areas such as artificial intelligence, robotics, Industry 4.0 and 5.0, intelligent transportation systems, digital twins, energy efficiency, environmental engineering, advanced materials, and digital transformation. Through analytical studies, experimental research, and case studies, the contributions address both technological development and real-world impact. Special emphasis is placed on sustainable and human-centric solutions, smart infrastructure, automation, and data-driven decision-making across industry, public administration, education, and services. This publication is intended for researchers, professionals, and decision-makers seeking insight into current technological trends and future development pathways.