Roslagsbanan is an 891 mm (2 ft 11 ¹⁄₁₀ in) (three Swedish feet) narrow-gauge urban railway system in Stockholm County, Sweden. Its combined route length is 65 kilometres (40 miles) and there are 39 stations. The line starts in Stockholm at Stockholms östra. It goes north and splits into three branch lines, terminating in Näsbypark, Österskär and Kårsta. It has double track between Stockholm and Viggbyholm, Åkers Runö and Åkersberga. The rest is single track. The railway is owned by the Stockholm county through Storstockholms Lokaltrafik, and is not a part of the nationally owned network.

Roslagsbanan is part of the Stockholm public transport system. It is operated under contract by Roslagståg AB, a joint venture by the Danish DSB and Tågkompaniet. The railway is quite popular considering its age and capacity. There are fifteen departures from Stockholms östra at afternoon rush hour, with a total ridership of 42,000 journeys per day.