巽他海峡
Cilegon is located on the most northwest coast of Java island, at the mouth of the Cilegon River on Ciwandan Bay, which is an inlet of the Sunda Strait. It is administratively a semi-enclave within Serang Regency, as it borders with Serang Regency in the east and south, while it borders with Sunda Strait in the north and west.