The Cranbourne line is a commuter railway line in the city of Melbourne, Victoria, Australia. Operated by Metro Trains Melbourne, it is the city's second longest metropolitan railway line at 44 kilometres (27 mi). The line runs from Flinders Street station in central Melbourne to Cranbourne station in the south-east, serving 24 stations via the City Loop, South Yarra, Caulfield, Oakleigh, and Dandenong. The line operates for approximately 20 hours a day with 24 hour service available on Friday and Saturday nights. During peak hour, headways of up to 5 to 15 minutes are operated with services every 15–20 minutes during off-peak hours. Trains on the Cranbourne line run with a seven-car formation operated by High Capacity Metro Trains.

Metro Trains Melbourne, often known simply as Metro, is the operator and brand name of train services on the electrified metropolitan rail network serving the city of Melbourne, Victoria, Australia. It is the largest urban rail network in Australia, with 17 lines and 221 stations across 405 km (252 mi) of railways, and the second busiest network in Australia, with a patronage of 99.5 million as of 2021–2022.