Nordsee-Treene is an Amt ("collective municipality") in the district of Nordfriesland, in Schleswig-Holstein, Germany. Its seat is in Mildstedt. It was formed on 1 January 2008 from the former Ämter Friedrichstadt (except the town Friedrichstadt), Hattstedt, Nordstrand and Treene.

The Amt Nordsee-Treene consists of the following municipalities:

Arlewatt Drage Elisabeth-Sophien-Koog Fresendelf Hattstedt Hattstedtermarsch Horstedt Hude Koldenbüttel

Mildstedt Nordstrand Oldersbek Olderup Ostenfeld Ramstedt Rantrum Schwabstedt Seeth

Simonsberg Süderhöft Südermarsch Uelvesbüll Winnert Wisch Wittbek Witzwort Wobbenbüll

54°27′42″N 9°05′43″E / 54.461667°N 9.095278°E / 54.461667; 9.095278