The Kolkata Metro is a rapid transit system serving the city of Kolkata and the wider Kolkata Metropolitan Region in West Bengal, India. Opening in 1984, it was the first operational rapid transit system in India, beside being the second busiest and fourth-longest metro network in India. As of March 2024, it has four operational lines: the 32.13 km (19.96 mi) Line 1 from Dakshineswar to Kavi Subhash, 14.1 km (8.8 mi) Line 2 from Salt Lake Sector V to Howrah Maidan, 7.75 km (4.82 mi) Line 3 from Joka to Majerhat and 5.4 km (3.4 mi) Line 6 from Kavi Subhash to Hemanta Mukherjee for a total of 59.38 km (36.90 mi). Two other lines are in various phases of construction and planning. The system has a mix of underground, at-grade and elevated stations using both broad-gauge and standard-gauge tracks. Trains operate between 06:55 and 22:30 IST and the fares range from ₹5 to ₹50.

Kolkata Metro Line 2, also known as the East-West Metro and Green Line, is a rapid transit line of the Kolkata Metro in the Indian state of West Bengal. It currently consists of two distinctly operational sections between Salt Lake and Sealdah, and Esplanade and Howrah Maidan by going underneath the Hooghly River, with an eastern extension planned for Teghoria. It will cover a distance of 32.11 km (19.95 mi) and consist of 17 stations from Teghoria (Haldiram) in the east to Howrah Maidan in the west, of which it will consist of 11 elevated and 6 underground stations, and the operational section consists of 6 elevated and 5 underground stations, with a total distance of 22 km (14 mi). It is expected to derive a very high ridership, since it will connect India's two largest commuter railway and long-distance railway terminals, Howrah and Sealdah, along with two of its largest business districts, BBD Bagh and Salt Lake Sector V. At present, more than 100,000 passengers commute through the line every day, and this figure is expected to go up to 1 million after it gets fully completed by 2035. It will also connect the industrial hub of Kolkata, i.e., Howrah and the IT hub of Kolkata, i.e., Salt Lake Sector-V. It connects Line 1 at Esplanade and will eventually connect Lines 3 and 6.