Ytre Hvaler National Park is a national park located within the municipalities of Hvaler and Fredrikstad in Østfold, Norway. The park was established on 26 June 2009 and was the first national marine park in the country of Norway. The park manager is located in Skjærhalden. Ytre Hvaler is mostly a marine park, covering the outer parts of the skerries of the east shore of Oslofjord. To the south, the national park's boundaries lie on the Norway–Sweden border next to Kosterhavet National Park.