Exo, officially known as Réseau de transport métropolitain (RTM; English: Metropolitan Transportation Network), is a public transport system in Greater Montreal, including the Island of Montreal, Laval (Île Jésus), and communities along both the North Shore of the Mille Îles River and the South Shore of the St. Lawrence River. It was created on June 1, 2017, taking over from the Agence métropolitaine de transport. The RTM operates Montreal's commuter rail and metropolitan bus services, and is the second busiest such system in Canada after Toronto's GO Transit. In May 2018, the former Réseau de transport métropolitain (RTM) was branded as Exo.

Exo's territory is concurrent with Montreal Metropolitan Community limits, with the addition of the Kahnawake First Nations reserve and the city of Saint-Jérôme. It serves a population of approximately 4.1 million people who make more than 750,000 trips daily in the 4,258.97 km² (1,644.40 sq mi) area radiating from Montreal.

Exo's mandate includes the operation of Montreal's commuter rail service, which links the downtown core with communities as far west as Hudson, as far east as Mont-Saint-Hilaire, as far south as Candiac, and as far north as Saint-Jérôme and commuter buses formerly operated by local operators.