The Chennai Suburban Railway is a commuter rail system in the city of Chennai, Tamil Nadu, India, operated by the Southern Railways branch of Indian Railways. It is the second largest suburban rail network in terms of route length and the third largest in terms of commuters in India. Around 1,000 services are operated daily between 4:00 a.m. and midnight. It is the longest suburban circular route in India covering of 235.5 km (146.3 mi).

Chennai has a complex railway network. It is the third busiest suburban rail system in India after Mumbai and Kolkata. It has separate tracks for local and express trains. The system uses electrical multiple units (EMUs) operating on alternating current (AC) drawn from overhead wires through the catenary system. The total system spans around 1,174.21 kilometres (729.62 mi) of which only 509.71 kilometres (316.72 mi) have dedicated dual tracks for suburban EMUs, the rest share tracks with other trains and are called mainline EMUs (MEMUs). As of 2013, the suburban sector has 1,000 services, including 250 in the Beach–Chengalpattu section, 240 services in the Chennai Central–Arakkonam section, and 90 in the Chennai Central–Gummidipoondi. As of 2020, 2.5 million people use the suburban train services daily and 401.72 million passenger every year. This includes 8,20,000 in the Beach–Tambaram section, 5,50,000 in the Central–Pattabhiram section, and 2,00,000 in the Central–Gummidipoondi section and 2,00,000 in the MRTS section. This is a 13.2 percent increase over the previous year. A total of 65 stations in the suburban section have bicycle stands.