Alnö bridge, Road bridge in Sundsvall Municipality, Sweden.

The Alnö Bridge is a 1,042-metre road bridge carrying Länsväg 615 over the Alnösund between Johannedal on the mainland and the island of Alnön. Its main span is a prestressed concrete box-girder bridge with seven spans, the longest 134 metres, rising 42 metres above the sound with 40 metres of clearance for shipping. The deck is 9.40 metres wide with two lanes and narrow pavements on both sides.

Construction began with the first sod turned on 6 April 1961, and the bridge opened to traffic on 24 October 1964. It replaced the car ferry that had previously carried people between Alnön and the mainland. Until the Öland Bridge opened in 1972, it was Sweden's longest bridge.

The bridge's mainland end lies at Johannedal, between Sundsvall and Sundsbruk, while on Alnön it leads into the island centre called Vi, Wii or Alnövi. Until 1964 cars crossed the Alnösund by ferry; the bridge replaced that crossing and is still the island's only link to the mainland.

The bridge carries two lanes of Länsväg 615 over the Alnösund, with narrow pavements on both sides. Clearance under the main span is 40 m, marked at night by beacons. Since 2008 railings stand over 2 m high, and SOS phones and surveillance cameras are fitted.

The bridge's guardrails were raised above 2 metres in 2008 to prevent suicides; before that, Alnöbron ranked third among Swedish bridges for suicides, after Angeredsbron and Älvsborgsbron in Gothenburg. Emergency phones and surveillance cameras were also installed.