The present study explores the strategic importance and multidimensional impact of Big Data on contemporary financial processes and financial technology (FinTech). As a fundamental technological component of the Fourth Industrial Revolution, together with artificial intelligence, machine learning and the Internet of Things, big data is transforming the manner in which financial institutions evaluate risk, personalise services and make data-driven decisions. The analysis is grounded in a comprehensive literature review, which includes a thorough review of international literature and institutional reports. The paper focuses on the five fundamental dimensions of Big Data (volume, velocity, variety, accuracy, value) and their application in credit assessment, fraud detection, and the development of personalised financial products. The findings emphasise the significance of Big Data in enhancing efficiency, innovation, forecasting, and customer-centric strategy in the banking and investment sector. In parallel, critical challenges are emphasised, particularly in the areas of privacy, algorithmic bias, and regulatory compliance. The study proposes a responsible data governance framework and provides recommendations for future cross-sectoral and empirical research, including the implementation of algorithmic transparency checks and social impact evaluations. The argument is made that the ethical and sustainability-focused integration of Big Data in FinTech is essential for market competitiveness and the promotion of a more equitable and digital economy.