Middle Mouse is an uninhabited island situated 1 kilometre off the north coast of Anglesey. It is notable as the northernmost point of Wales. The island measures a maximum of 207 metres by 110 metres, with a maximum area of 3.7 acres and has a maximum altitude of 16 metres above sea level. It is one of a chain of three islands off the north of Anglesey, the others being West Mouse and East Mouse.
The S.S. Liverpool following a collision with a ship named ‘Laplata’ was shipwrecked near Middle Mouse in 1863.She had on board a shipment of tin ingots.
In 2005, the island was put up for sale as part of a 168-acre (0.68 km2) estate.