The book’s philosophy is around using artificial intelligence-, IoT-, and blockchain-based technologies to improve smart city applications. This chapter covers blockchain technology, ensuring that readers grasp its ideas, components, and significance to smart cities. It lays the foundation for subsequent chapters that delve deeper into the connections between these technologies and how they can be used in practice. Blockchain systems are decentralized (distributed) ledger systems that guarantee that transactions across nodes in a network are safe, transparent, and final without the need for intermediaries. Its basic components include supply chain administration, financial services, healthcare, consensus algorithms, and smart contracts. All of these encourage accountability and authority through a wide range of fields. Blockchain innovation decreases dependence on an administrative authority and creates an adequate framework for growth security, eliminating illegal activities, and developing accuracy in digital transactions. As blockchain grows further, it has the potential to completely transform many sectors by providing cutting-edge answers to persistent problems with trust and data management. Finally, regulatory and ethical considerations are presented, emphasizing the importance of legal frameworks and ethical guidelines in deploying blockchain technology. By establishing a solid foundation in blockchain technology, this chapter prepares readers for subsequent discussions on an overview of blockchain technology, fundamentals of concepts of blockchain, its architecture, versions, and its SWOC analysis.