Usedom (German: Usedom [ˈuːzədɔm], Polish: Uznam [ˈuznam]) is a Baltic Sea island on the border between Germany and Poland. It is situated north of the Szczecin Lagoon (German: Stettiner Haff) estuary of the River Oder in Pomerania. Most of the island belongs to the German district of Vorpommern-Greifswald in the Federal State of Mecklenburg-Vorpommern, with the exception of the eastern part and the city of Świnoujście (German: Swinemünde) which is in Polish West Pomeranian Voivodeship. Its area is 445 km² (the German part 373 km²; the Polish part 72 km²).

Its population is 76,500 (the German part 31,500; the Polish part 45,000).

The island is separated to the east from the neighbouring island of Wolin by the Świna (German: Swine) strait (or river), which is the main route connecting Szczecin Bay with the Pomeranian Bay, a part of the Baltic Sea. The strait between the island and the mainland is called the Peenestrom; it is a downstream extension of the valley of the Peene river, which flows into the westernmost part of the Stettin Lagoon. The island is mostly flat, partly covered by marshes.