Open Educational Resources (OER) have the potential to significantly contribute to achieving Sustainable Development Goal 4 (SDG 4) by expanding access to education and promoting global educational equity. This chapter, which draws on a review of primary and secondary literature, examines how OER initiatives support marginalized communities and regions with limited infrastructure by providing open access to high-quality educational materials. These initiatives foster inclusive, learner-centered education and facilitate lifelong learning, making education more adaptable and accessible across diverse contexts. The chapter also explores the sustainability of OER, addressing key factors such as user-created content, quality assurance processes, cost-effectiveness, and the role of open licensing in maintaining the relevance and accessibility of resources. Given the challenges surrounding the widespread adoption of OER, this chapter examines key issues such as disparities in digital access, concerns about resource quality, and the need for effective instructional approaches. It also proposes strategies for addressing learners’ individual needs and highlights the critical importance of designing rigorous assessments to accurately measure the impact of OER.