Thane District is a district in the state of Maharashtra in Konkan Division. At the 2011 Census it was the most populated district in the nation, with 11,060,148 inhabitants; however, in 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 Navi Mumbai, Kalyan-Dombivli, Mira-Bhayander, Bhiwandi, Ulhasnagar, Ambarnath, Badlapur, Murbad and Shahapur. 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.

In 1817, the territory now comprising Thane district was taken over by the British from the Peshwa and it became a part of North Konkan district, with its headquarters in Thana. Since then, it has undergone considerable changes in its boundaries. In 1830, the North Konkan district was expanded by adding parts of South Konkan district and in 1833 was renamed Thana District. In 1853, the three sub-divisions of Pen, Roha and Mahad together with Underi and Revadanda agencies of Kolaba were formed into the sub-collectorate of Kolaba, under Thana, and ultimately were separated to become an independent Kolaba district in 1869 (now known as Raigad district).

Back in 1866, the administrative sub-divisions of Thana were reorganised and renamed: Sanjan as Dahanu, Kolvan as Shahapur and Nasrapur as Karjat. Vada petha was upgraded to the level of a taluka. Uran Mahal was separated from Salsette in 1861 and was placed under Panvel. Panvel, together with its mahals of Uran and Karanja, was transferred to Kolaba district in 1883 and Karjat was transferred in 1891. A new mahal with Bandra as headquarters was created in 1917 and in 1920 Salsette was divided into two talukas — North Salsette and South Salsette. South Salsette consisting of 84 villages was separated from Thana District and included in the newly created Bombay Suburban district (present Mumbai Suburban district). North Salsette was made a mahal under Kalyan taluka in 1923 and renamed as Thana in 1926. Kelve-Mahim was renamed as Palghar. 33 villages of the Bombay Suburban district were transferred to Thana district in 1945 and 14 of them were re-transferred to the Bombay Suburban district in 1946 when the Aarey Milk Colony was constituted.

After Independence, in 1949, the princely state of Jawhar was merged with Thana district and became a separate taluka. As many as twenty-seven villages and eight towns from Borivali taluka and one town and one village from Thana taluka were transferred to the Bombay Suburban district in 1956 when the limits of Greater Bombay were extended northwards in Salsette. In 1960, following the bifurcation of the bilingual Bombay State, 47 villages, and three towns in the taluka of Umbargaon were transferred to Surat district in Gujarat and its remaining twenty-seven villages were first included in Dahanu and later in 1961 made into a separate mahal, Talasari. In 1969, the taluka of Kalyan was divided into two talukas, Kalyan and Ulhasnagar.

The district is the northernmost part of the Konkan lowlands of Maharashtra. It comprises the wide amphitheatre like Ulhas basin on the south and hilly Vaitama valley on the north together with plateaus and the slopes of Sahyadri. From the steep slopes of the Sahyadri in the east, the land falls through a succession of plateaus in the north and centre of the district to the Ulhas valley in the south. These lowlands are separated from the coast by a fairly well-defined narrow ridge of hills that runs north-south to the east of the Thane creek, parallel to the sea, keeping a distance of about 6 to 10 km from the shores. Isolated hills and spurs dot the district area.

According to the 2011 census Thane district has a population of 11,054,131, roughly equal to the nation of Cuba or the US state of Ohio.This gives it a ranking of 1st in India (out of a total of 640) and 1st in its state.The district has a population density of 1,157 inhabitants per square kilometre (3,000/sq mi).Its population growth rate over the decade 2001-2011 was 35.94%.It has a sex ratio of 880 females for every 1000 males, and a literacy rate of 86.18%.

It had a population of 8,131,849 of which 72.58% were urban as of 2001.Total literacy rate of the district is 80.67% (male 87.06% and female 73.10%). The population of Thane district in 2011 had risen to 11,054,131; this is close to 10 percent ( 9.84 ) of Maharashtra’s estimated population of 112.4 million and 1% of India’s Total population.It is the most populated district in the country, somewhat ahead of North 24 Parganas district in West Bengal which had 10,082,852 people.The density of population was estimated at 1,157 people per square kilometre. The sex ratio i.e. number of females per 1000 male was 880 which is less than the states average of 925 and the national average of 940.

The southern talukas are the mostly urban areas, Marathi is main language and also due to migration many other languages like Urdu, Sindhi, Gujarati and Hindi are spoken. Marathi is the main language and is only language in the rural talukas.Western coastal region is mostly populated by Kolis, the northern and the eastern talukas are populated by the Varlis, known for making stark images from red mud on house walls.

According to the 2001 Census, the total working population in the district was 11,961,704 persons, which is 47.37% of the total population of the district. Out of total working force, 51.75% were engaged in agriculture and allied activities, 6.19% in manufacturing, service and cottage industries and remaining 30.69% in other activities. Out of total working force, the female working force was 22.89% in the district.

The Thane Municipal Corporation started its own public transport service known as the Thane Municipal Transport (TMT) from February 9, 1989. The TMT has a fleet of 289 buses which ply on 45 routes from 2 bus-depots and 8 bus-stands ferrying approximately 2.8 lakhs commuters daily.In 2006, Mira Bhayandar Municipal Corporation (MBMT) commenced its own public transport service, known as the Mira-Bhayandar Municipal Transport. The Kalyan Dombivli Municipal Corporation also runs its own Kalyan-Dombivli Municipal Transport (KDMT) service. Maharashtra State Road Transport Corporation (MSRTC) buses connect Thane city to different parts of the district and also to other districts. BEST provides services to Suburban Mumbai, Thane city and Mira Bhanyandar.

The total railway track length in the district is 345.73 km. spread in western and central part of the district. The Western Railway network passes through Vasai, Palghar and Dahanu talukas of the district and Central railway network passes through Thane, Kalyan, Ulhasnagar and Shahapur talukas of the district. Western Railway local trains leaving from Churchgate railway station go up to Dahanu Road railway station in the district. Central Railway local trains leaving from Chhatrapati Shivaji Terminus go up to Kalyan, Ambarnath, Badlapur, Karjat and Kasara. In 1994, a new connection made from Diva Junction to Vasai. This connection joined Central Railway and Western Railway networks and its length is 41.96 km.[15] Konkan Railway network also passes through a part of the district. Local trains have now started plying from Chhatrapati Shivaji Terminus, Mumbai to Panvel on this network. Dahanu, Satpati, Mahim. Kalyan, Vasai, and Uttan are the ports on the Arabian Sea coast. Ferry services are available between these ports. Metered Auto Rickshaws ply in Thane, Mira-Bhyander and several other towns. Metered Taxi services are also available in Thane, Mira-Bhayandar and some other towns.