Lake Orestiada or Lake Kastoria (Greek: Λίμνη Ορεστιάδα) is a lake in the Kastoria regional unit of Macedonia, northwestern Greece. Sitting at an altitude of 630 metres, the lake covers an area of 28 square kilometres. Nine rivulets flow into the lake. Its depth varies from nine to ten metres. The Orestida was formed about 10 million years ago. The Kastoria Peninsula (with the town of Kastoria) divides the lake into two parts, the larger to the north and the smaller to the south.