The rapid pace of urban growth in the 21st century has transformed cities into complex and interconnected systems that extend far beyond their municipal boundaries. As urbanisation intensifies, the terminology associated with city expansion-particularly metropolitan areas and metropolitan regions is frequently used interchangeably, even though they represent conceptually distinct spatial, functional, and governance entities. Understanding the difference between these two frameworks is essential in urban and regional planning, transport planning, public policy, and sustainable development. This paper provides a comprehensive comparative analysis of metropolitan areas and metropolitan regions by examining their definitions, boundaries, functional characteristics, governance structures, socio-economic influence, and planning implications. Drawing insights from global examples and detailed case studies from India-including Delhi NCR, Mumbai MMR, and Bengaluru BMR-the paper highlights key similarities and contrasts and argues that while metropolitan areas represent the compact, continuous urban footprint, metropolitan regions reflect a broader sphere of economic, functional, and socio-spatial influence extending into peri-urban and rural territories. The study underscores the importance of adopting regionally integrated planning approaches to address contemporary challenges, such as transportation connectivity, land-use fragmentation, environmental stress, and socio-economic disparities. It concludes by emphasizing the need for coordinated governance models and integrated metropolitan regional planning frameworks to support sustainable urban futures.