Thane District is a district in northern Maharashtra state in western India. At the 2011 Census it was the most populated district in the nation, with 11,060,148 inhabitants; however, in 2014 the district was split into two with the creation of a new Palghar district, leaving the reduced Thane district with a 2011 Census population of 8,070,032. The headquarters of the district is the city of Thane. Other major cities in the district are Kalyan-Dombivli, Mira-Bhayander, Bhiwandi, Ulhasnagar, Ambarnath, Kulgaon-Badlapur, Shahapur and Navi Mumbai. This is the third-most industrialised district in Maharashtra.
The district is situated between 18°42' and 20°20' north latitudes and 72°45' and 73°48' east longitudes. The revised area of the district is 4,214 km². The district is bounded by Pune and Ahmadnagar districts to the east, and by Palghar district to the north. The Arabian Sea forms the western boundary, while it is bounded by Mumbai City District and Mumbai Suburban District to the southwest and Raigad District to the south.