Stephenson Island, also called Mahinepua Island, is the larger of a pair of small islands off the northern coast of New Zealand in Whangaroa Bay. It is approximately long and wide, positioned with the major axis running northwest to southeast. The area is . Immediately to the northwest lies the smaller Cone Island. Satellite imagery indicates that the islands are partially forested and contain only two sites with buildings as discernible signs of habitation.
Land Information New Zealand records show that the islands are jointly owned by eleven families and are classified as Maori Land.
The MÃÂori name for Stephenson Island is Mahinepua Island, which is rarely seen on maps; both are official names for the island. The highest point is Ririwha, at elevation.