The S3 is a commuter rail route forming part of the Milan suburban railway service (), which converges on the city of Milan, Italy.
The service runs over the MilanâÂÂSaronno railway, the oldest line owned by the Ferrovie Nord Milano. Like all other Milan suburban railway service routes, it is operated by Trenord.
Line S3, a radial route, runs from Saronno in a south easterly direction, via the MilanâÂÂSaronno railway, to Milano Cadorna, the railway's urban terminus. The travel takes 35 minutes.
The S3 was incorporated into the suburban service on 12 December 2004.
The stations on the S3 are as follows (stations with blue background are in the municipality of Milan):
, S3 trains ran every thirty minutes between 06:00 and 01:00 daily.