Lake Orestiada or Lake Kastoria is a lake in the Kastoria regional unit of Macedonia, northwestern Greece. Sitting at an altitude of 630 meters, the lake covers an area of 28 square kilometers.
Nine rivulets flow into the lake. Its depth varies from nine to ten meters. The Orestiada was formed ca. 10 mya 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.
The lake takes its name from the Oreiades. Lakeside attractions include, apart from the Byzantine architectural heritage of the town, an 11th-century Byzantine monastery of Panagia Mavriotissa and the reconstructed prehistoric settlement of Dispilio, where the Dispilio Tablet was retrieved from the lake in 1992.