Haig Fras is a 45 km long submarine granitic rocky outcrop in the southern part of the Celtic Sea, lying about 95 km northwest of the Isles of Scilly. It covers an area of 356.5 square kilometres (137.6 sq mi). At one point it reaches within 38 m of the sea surface. It is protected as a Special Area of Conservation (SAC) because of the diverse fauna developed in its bedrock reef habitat.