The Sarmiento line is a broad gauge commuter rail service in Buenos Aires Province, Argentina, run by the state-owned Trenes Argentinos since 11 September 2013.

After the Government of Carlos Menem privatized the urban railways services, consortium Trenes de Buenos Aires (TBA) took over the Sarmiento and Mitre lines.

[13] The works, which also included the installation of a communications-based train control system, meant that the line was closed on Sundays from February to June of that year on its electrified segment, with replacement bus services operating during that time.

Nowadays it is only used for freight to the Port of Buenos Aires, being operated by private company Ferrosur Roca; however, it was briefly used for passenger services in the 1990s.

Construction of the tunnel had been initiated by the Buenos Aires Western Railway in 1912; however, it was not completed until 1916 due to delays caused by the First World War.

Under plans announced in 2006, a 33 km tunnel would be bored between Moreno and Caballito in order to replace the surface alignment of the Sarmiento commuter route.