The given research paper investigates the revolutionary impact of digital technologies on the redefinition of modern human resource management. The research incorporates Artificial Intelligence (AI), Big Data Analytics, and e-HRM systems to investigate the way Smart HR 4.0 can lead to job satisfaction, business performance, and organizational sustainability. It puts more focus on how automation and data-driven HR practices empower, engage, and give autonomy to employees, which eventually increases their satisfaction and retention. Additionally, Smart HR 4.0 supports real-time decision making, business agility and innovation, which enhances the overall business performance. Green HRM and Circular Economy are also incorporated into the paper and the authors demonstrate how HR practices facilitated by technology may reconcile digital transformation with agility towards the environment and long-term sustainability. The mediating variables like business intelligence and organizational culture have been identified to be relevant in ensuring the maximization of the Smart HR implementation. The research adds the conceptual framework in how digital transformation relates to sustainable human resource development to facilitate flexibility, inclusiveness, and resilience in changing organizational environments. In general, Smart HR 4.0 can be seen as a strategic requirement and as a driver of sustainability, making organizations successful in the digital world.