Erdek is a municipality and district located in the Balıkesir Province of Turkey. Situated on the Kapıdağ Peninsula, it lies along the north coast of the Gulf of Erdek at the southern edge of the Sea of Marmara. The district encompasses an area of 307 km2 and has a population of 32,021 as of 2024.
The region is characterized by rugged geology and topography, featuring large olive groves and evergreen wooded areas. It is geographically dominated by Mt Dindymus, which reaches an elevation of 782 meters. The Erdek district also includes the islands of Koyun and Paşalimanı.
Erdek serves as a popular domestic holiday destination in Turkey. The area features several hotels that date back to the 1960s to accommodate visitors to the coast.