Azienda Trasporti Milanesi (ATM) is a public company, responsible for public transportation in Milan city and some surrounding municipalities, in Italy. It operates 18 tram lines, part of which are run with Peter Witt streetcars from the 1920s, 82 urban Bus lines, 4 Trolleybus lines, 35 interurban Bus lines, 4 underground lines (Metropolitana di Milano), carrying over 734 million passengers in 2010.

ATM offers also other minor services mainly related to transportation around the city. These services include Radiobus, an on-call minibus service; the light railway linking the San Raffaele Hospital with the line 2 underground; the Como–Brunate funicular railway; Guidami car sharing and BikeMi bike sharing services.