The integration of circular economy principles within Sustainable Enterprise Resource Planning (S-ERP) in Industry 4.0 represents a transformative approach to enhancing resource efficiency, sustainability, and innovation across business functions. This chapter explores the synergy between circular economy strategies and advanced digital technologies such as the Internet of Things (IoT), artificial intelligence, and blockchain within S-ERP systems. By embedding circular economy principles into the core of business operations—ranging from product design and supply chain management to production processes and lifecycle assessments—organizations can significantly reduce waste, optimize resource use, and extend product lifecycles. The chapter also presents formal models and methodologies that leverage situation awareness, fuzzy logic, and decision support systems to facilitate the adoption of circular economy practices in Industry 4.0. Additionally, it discusses the challenges and opportunities associated with implementing these strategies, offering practical solutions to overcome barriers such as data inconsistency, technological integration, and regulatory compliance. Through a comprehensive analysis, this chapter aims to provide a robust framework for businesses to achieve sustainable growth and competitiveness in the evolving digital and environmental landscape.