The line S12 () 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, MilanâÂÂBologna and Milan-Asso railways. Like all but one of the other Milan suburban railway service routes, it is operated by Trenord.
Line S12, a cross-city route, heads initially in a southerly direction from Milano Bovisa through the Milan Passante railway to Milano Rogoredo. From there, it turns south-east towards its southern terminus, Melegnano.
The route was activated on 12 September 2016. The route was suspended on 25 February 2020 due to COVID-19 pandemic and it has been partially restored in August 2023, with four trains per direction per day, running at 15 minutes intervals when paired with line S1. A more complete service shall be restored in 2024: since June 2024, service has been expanded, with 10 round trip per day from Cormano-Cusano Milanino to Melegnano and one round trip per day between Cormano-Cusano Milanino and Milano Rogoredo; this has been made possible by the construction and opening of the third track from Milano Affori to Cormano-Cusano, allowing for more separation between regional trains, which run express from Affori to Cesano Maderno, and suburban all-stopping trains.
The stations on the S12 are as follows (stations with a coloured background are within the municipality of Milan):