Big data systems enable large-scale collection, storage, processing, and analysis of personal information across global digital ecosystems. As data travels across jurisdictions with different legal norms, international privacy frameworks become essential to protect user rights, regulate data flows, and reduce cyber risks. This study analyzes various international privacy regimes, including GDPR (EU), CCPA (USA), PDPB (India), PDPA (Singapore), LGPD (Brazil), PIPL (China), and OECD cross-border principles. Using comparative analysis, regulatory interpretation, and hypothetical datasets, the paper evaluates how differing legal definitions, enforcement mechanisms, and cultural norms shape global data governance. Results show that global harmonization is hindered by political sovereignty, economic interests, and technological complexity. A unified policy model is proposed to balance innovation, security, and human rights.