Cyzicus (Greek: Κύζικος) was an ancient town of Mysia in Asia Minor, situated on the shoreward side of the present peninsula of Kapu-Dagh (Arctonnesus), which is said to have been originally an island in the Sea of Marmara, and to have been artificially connected with the mainland in historic times.

Now, Cyzicus is protected by the Republic of Turkey's Ministry of Culture, and located on the Erdek and Bandırma roads in Turkey.