Heigham Holmes is a national nature reserve located within the Norfolk Broads in the English county of Norfolk. The reserve is, in effect, an island, being surrounded by the river channels, drainage ditches and wetland areas of the Broads. It is only accessible by an unusual floating swing bridge across the River Thurne from the village of Martham. The reserve is owned by the National Trust and is within the Broads National Park and the civil parish of Potter Heigham. It is only opened to the public for one day a year.