Kalyan (Marathi: ) is a city in Thane district of Maharashtra, and a major railway station lying at the junction of the north-east and south-east lines of the suburban Mumbai division of the Central Railway, 53 km north-east of Mumbai. Kalyan is also a major Taluka place, a tehsil of the Thane district. With its neighbouring township of Dombivli, Kalyan jointly forms the Kalyan-Dombivli Municipal Corporation, abbreviated as KDMC. It is considered a part of the Greater Mumbai metropolitan agglomeration, along with Navi Mumbai and the cities of Bhiwandi, Thane, Ulhasnagar and the municipal councils of Ambernath & Badlapur.
Kalyan is a port for more than two millennia until siltation and the rise of Mumbai eclipsed it and its sister ports, Nallasopara, Thane, Vasai, etc. The port was ruled by the Maurya and Gupta Empires of North India and later was part of a petty Konkan principality vassal to the Yadava dynasty of Deogiri. Extensive ruins in Kalyan indicate the city's former magnificence.