Mumbai Metropolitan Region (MMR) is a metropolitan area consisting of the metropolis of Mumbai and its satellite towns in Maharashtra. Developing over a period of about 20 years, it consists of seven municipal corporations and fifteen smaller municipal councils. The entire area is overseen by the Mumbai Metropolitan Region Development Authority (MMRDA), a Maharashtra State Government organisation in charge of town planning, development, transportation and housing in the region. The MMRDA was formed to address the challenges in planning and development of integrated infrastructure for the metropolitan region. The areas outside of Brihan Mumbai (Greater Mumbai) and Navi Mumbai have lacked organised development. Navi Mumbai, developed as one of the largest planned cities in the world, was promoted by a Maharashtra Government-owned company, City and Industrial Development Corporation (CIDCO). The region has had problems related to haphazard and illegal development as a result of rapid urbanisation. Villages along the NH3 in Bhiwandi Taluka are examples of haphazard developments in the MMR, with some of the largest warehousing areas in India. Government agencies such as the Town Planner and Collector of Thane have had challenges in addressing unorganised development.
The region has an area of 4,355 km² and with a population of 20,748,395, it is among the list of urban agglomerations by population (United Nations)|top ten most populated urban agglomerations in the world. It is linked with Mumbai through the Mumbai Suburban Railway system and a large network of roads.