The Lilydale line is a commuter railway line in the city of Melbourne, Victoria, Australia. Operated by Metro Trains Melbourne, it is the city's sixth-longest metropolitan railway line at 37.8 kilometres (23.5 mi). The line runs from Flinders Street station in central Melbourne to Lilydale station in the east, serving 27 stations via Burnley, Box Hill, Ringwood, and Croydon. The line operates for approximately 19 hours a day with 24 hour service available on Friday and Saturday nights. During peak hours, headways of up to 15 minutes are operated, with services every 20–30 minutes during off-peak hours. Trains on the Lilydale line run in two three-car formations of X'Trapolis 100 trainsets.

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.