Hammarby sjö (Swedish: "Lake Hammarby") is a watercourse in central Stockholm, Sweden. Separating Stockholm City Centre from South Stockholm, or, more locally, Norra Hammarbyhamnen on eastern Södermalm from, it connects Saltsjön to Årstasjön.
Covering a surface of 34 hectares and having an average depth of 4.5 metres (maximum 6 metres), Hammarby sjö is supplied by a drainage area covering 159 hectares and contains 1,600,000 cubic metres of water. Originally a lake about 3 metres deep, it was transformed into a canal when connected to Saltsjön in the 1920s and a 6 metres deep channel was dug between and Saltsjön and another to . The importance of the water expanse has grown since the late 20th century as new residential areas have been constructed along its shores.[1]
Four bridges stretch over Hammarby Sjö and connected bodies of water: Danviksbron, Skansbron, Skanstullsbron and Johanneshovsbron.