Annotation: The article examines the role of blockchain technology in transforming financial transactions and the e-commerce sector. It considers theoretical foundations, consensus algorithms, as well as international and Ukrainian case studies. Key blockchain platforms (Bitcoin, Ethereum, Ripple, Hyperledger) are analyzed and compared with traditional payment systems (Visa, Mastercard). International use cases (Amazon, IBM Food Trust, Walmart–Hyperledger) and Ukrainian examples (Prozorro, Diia City, e-hryvnia) are presented. Particular attention is paid to scalability issues, environmental challenges, cyber risks, and regulatory barriers. Practical recommendations for blockchain implementation in the Ukrainian financial and trade sectors are provided.