Kalyan is a central line suburb of Mumbai, India. It ia a part of Greater Mumbai agglomeration.

Kalyan city is located by the estuary of the Ulhas River with access to the Arabian Sea. Kalyan is 48 km (30 mi) northeast of Mumbai and is part of the Greater Mumbai area. Overcrowding in Mumbai and incentives from the government to develop areas outside of Mumbai have attracted industrial business as well as industrial employees to Kalyan.

Kalyan junction railway station is a very important station for suburban travel as well as for long distance trains.The line splits into two at Kalyan junction, one heads south-east for Karjat, the other heads north-east for Kasara .

On the eastern side of the city is a large industrial complex where electrical equipment, rayon, and dyes and other chemicals are manufactured. There are also a large number of textile-based cottage industries.

Kalyan was a port back in the Gupta dynasty . Extensive ruins in Kalyan indicate the city's former magnificence. It was occupied by the Bijapur sultanate (a Muslim state) in the 1500s and later by the Mughal emperor Shah Jahan, who fortified the city in the mid-1600s. Later the Marathas occupied the area, making Kalyan one of their strategic centers because it guarded the entrance to Bombay and the western coast of India. After the British defeated the Marathas at the end of the 18th century, Kalyan became part of the Bombay Presidency, a British province that became Bombay state after India's independence in 1947.

On the lighter side, Kalyan together with sibling town Dombivali is referred in local slang as Kandom. In 1982 the combined municipal corporation of Kalyan-Dombivali was formed to govern the two towns.