Schlei-Ostsee is an Amt ("collective municipality") in the district of Rendsburg-Eckernförde, in Schleswig-Holstein, Germany. Its seat is in Eckernförde, itself not part of the Amt. It was formed on 1 January 2008 from the former Ämter Schlei, Schwansen and Windeby.

The Amt Schlei-Ostsee consists of the following municipalities:

54°34′59″N 10°00′00″E / 54.583°N 10.000°E / 54.583; 10.000