The Zuiderzee Works is a system of dams and dikes, land reclamation and water drainage work, which was the largest hydraulic engineering project undertaken by the Netherlands during the twentieth century. The project involved the damming of the Zuiderzee, a large, shallow inlet of the North Sea, and the reclamation of land in the newly enclosed water using polders. Its main purposes are to improve flood protection and create additional land for agriculture.

The IJsselmeer, also known as Lake IJssel in English, is a closed-off inland bay in the central Netherlands bordering the provinces of Flevoland, North Holland and Friesland. It covers an area of 1,100 km2 (420 sq mi) with an average depth of 4.5 m (15 ft). The river IJssel, which is what the lake was named after flows into the IJsselmeer.