Väddö is an island in the Baltic Sea in Roslagen district, Sweden. It is situated in Norrtälje Municipality. Together with the adjoined Björkö it is considered the seventh largest island of Sweden.
Väddö is separated from the mainland by the artificial Väddö Canal, first dug in the 16th century.
The Stockholm Archipelago (Swedish: Stockholms skärgård) is the largest archipelago in Sweden, and the second-largest archipelago in the Baltic Sea (the largest being the Archipelago Sea across the Baltic in Finland). Part of the archipelago has been designated as a Ramsar site since 1989.
Stockholm Archipelago has been found to have slightly over 24,000 islands, islets and skerries and covers approximately 1,700 km² of which approximately 530 km² is land. There are around 10,000 permanent residences and 50,000 holiday homes in the archipelago. Residents are found on all the larger islands closest to the coast that have fixed bridges or ferry connections with road ferries, such as Vaxholm, Ingarö, Värmdö, Yxlan, Blidö, Ljusterö and Väddö, but also on many of the larger islands farther out from the coast, as Ingmarsö, Möja, Runmarö, Nämdö, Ornö and Utö, which are served by passenger ships with fixed itineraries.
The Väddö Canal (Swedish: Väddö kanal) is an artificial canal first dug in the 16th century to provide a sheltered passage between the Bagghusfjärden to the south and the Väddöviken to the north. The canal separates the island of Väddö from the mainland, and passes through the village of Älmsta at its northern end, and the lake of Storfjärden towards its middle.
The canal has an official depth of 2.0 metres and is mainly used by leisure boats, with some 20,000 boats passing through every year. There are no locks, but there are two opening bridges, the Älmstabron and the Bagghusbron.
Eckerö is a municipality of Åland, an autonomous territory under Finnish sovereignty. The municipality has a population of 959(30 June 2025) and covers an area of 752.67 square kilometres (290.61 sq mi) ofwhich 644.94 km (249.01 sq mi)is water. The population density is8.9 inhabitants per square kilometre (23/sq mi).
The municipality is unilingually Swedish and 86.5% of the population are Swedish speakers. It is the westernmost municipality of Åland and Finland.The company Eckerö Linjen operates a ferry connection between Berghamn in Storby, Eckerö and Grisslehamn on Väddö, Norrtälje in Sweden.