The Great Island is a common nickname for Madagascar, see also Great Island, Falkland Islands .

Great Island (Oileann Mor an Barraigh in Irish) is the name of an island in Cork Harbour, just outside Cork city, at the mouth of the River Lee. The town of Cóbh is situated on the island, which is connected by causeway to Fota Island to the north, which in turn is connected by causeway to the mainland. A railway line runs out through both islands to Cóbh.

The island's name comes from the Irish, meaning "Great island of the Barrys", referring to a powerful Norman family who settled in the area. The original name of the island was Oilean Ard na Neimhad, the "High (or important) island of Neimhad". Neimhad was a leader who invaded Ireland in ancient times.