Berezan (Cyrillic: Березань; Ancient Greek: Borysthenes; former Turkish: Pirezin) is an island in the Black Sea at the entrance of the Dnieper-Bug Estuary, Ochakiv Raion, Mykolaiv Oblast, Ukraine. It is often being confused with the artificial island of Pervomaisky that is located within Dnieper-Bug Estuary. The Berezan island measures approximately 900 metres in length by 320 metres in width.