Abstract Background: Engine-driven nickel-titanium (NiTi) instruments have significantly enhanced the safety and efficiency of root canal preparation. Their superelasticity and shape memory allow for safer and more predictable canal shaping. Aim: To provide an in-depth review of the historical development, classification, and comparative analysis of the five generations of NiTi rotary instruments, including the latest single-file systems. Methodology: A comprehensive review of existing literature and innovations in NiTi rotary endodontic instruments was undertaken, focusing on design, material, and mechanical improvements. Results: Five generations of rotary systems have been developed, each offering advancements in flexibility, cutting efficiency, fatigue resistance, and simplicity. Single-file systems mark a significant shift toward minimalism and efficiency in endodontic practice. Conclusion: NiTi rotary instrumentation has revolutionized endodontics, offering safer, faster, and more effective root canal shaping, with future trends likely focused on intelligent, adaptive file systems.