In 1867 the Prussian administration established twenty districts in its province of Schleswig-Holstein, among them the districts of Rendsburg and Eckernförde. The present district was established in 1970 by merging the former districts.
The district is situated at the coast of the Baltic Sea, roughly between the cities of Schleswig and Kiel. A large portion of the Kiel Canal passes through Rendsburg-Eckernförde. It is one of the largest districts in the whole of Germany.