The S13 is a commuter rail route forming part of the Milan suburban railway service (), which converges on the city of Milan, Italy.
The route runs over the infrastructure of the Milan Passante and Milan-Genoa railways. Like all but one of the other Milan suburban railway service routes, it is operated by Trenord.
Line S13, a cross-city route, heads initially in a southerly direction from Milano Bovisa-Politecnico through the Milan Passante railway to Milano Rogoredo. From there, it turns southwest towards its southern terminus, Pavia.
The route was activated on 11 December 2011, to coincide with the introduction of the 2011/12 winter timetable. It replaced the S10, which was simultaneously closed down.
The stations on the S13 are as follows (the stations with a coloured background are within the municipality of Milan):
, S13 trains ran at half-hourly intervals between 05:30 and 23:30 Monday to Friday, and at the same intervals on Saturdays and holidays between 06:00 and 19:00.
As of 2024, trains run half-hourly every day, with frequency reduced to hourly in late evening.