This chapter explores the theoretical foundations, models, and frameworks of blended learning by synthesising an extensive range of research literature. The chapter starts with critically examining the evolution of the notion of blended learning and the ongoing scholarly efforts to define it amidst its inherent complexities and varied contextual understandings. Through a critical discussion of the various definitions, the chapter reaffirms that blended learning is an umbrella term and an evolving concept. The chapter then outlines the rationale behind adopting blended learning, highlighting its capacity to cater to diverse learning preferences, enhancing accessibility and flexibility, and facilitating efficient and effective learning. It presents evidence from various studies demonstrating blended learning's potential to improve learning outcomes, foster active and deeper learning, and enhance student engagement and motivation. A critical focus of this chapter is the discussion of foundational theories supporting blended learning, including the Cognitive Theory of Multimedia Learning, Connectivism, Systems Theory, the Theory of Affordances, and the ARCS Model of Motivation. These theories provide a robust theoretical foundation that highlights blended learning not merely as a logistical or technological innovation but as a pedagogically driven approach, rooted in a deep understanding of how individuals learn in varied and interconnected environments. This theoretical diversity also justifies the adoption of blended learning across educational contexts and guides its continuous evolution to meet the diverse needs and preferences of learners. Following the theoretical foundation, the chapter outlines different models of blended learning, from the Face-to-Face and Online Driver models to new configurations like the Rotation, Flex, Self-Blended, Enriched Virtual, and Emergency Remote Teaching models, each tailored to specific learning objectives and contexts. The chapter also discusses the Community of Inquiry (COI) framework, the Complex Adaptive Blended Learning System (CABLS) Framework, and UNESCO’s Framework for Building the Capacity of Higher Education Institutions for Blended Learning for implementing blended learning effectively and efficiently. By providing a comprehensive overview of blended learning's theoretical underpinnings, practical models, and frameworks for adoption, this chapter advocates for embracing blended learning as a dynamic and evolving approach to the changing education landscapes.