The imperative for robust healthcare data privacy and security is escalating as healthcare systems worldwide are increasingly digitized. This review paper presents a comprehensive comparative analysis of the regulatory frameworks, challenges, and best practices related to healthcare data privacy and security in the United States and Nigeria. By examining the Health Insurance Portability and Accountability Act (HIPAA) in the US and the Nigeria Data Protection Regulation (NDPR) alongside other local regulations, this study highlights the nuances of each country's approach to safeguarding patient data. The analysis extends to the effectiveness of technological solutions like encryption and blockchain, and assesses the role of governance in policy implementation. Case studies from both nations offer insights into successful strategies and underscore the gaps and opportunities for cross-country learning and improvement. The paper concludes with targeted recommendations for policymakers and healthcare providers, aiming to strengthen the security measures and propose areas for further research and development in healthcare data management. This comparative study not only sheds light on current practices but also charts a course for future collaborative efforts to enhance data privacy and security in healthcare on a global scale.