Mosquito Island House, Stone house in St. George, United States.

Mosquito Island House is a 1+1⁄2-story Cape-style house on Mosquito Island, about 2 miles south of Martinsville, Maine. It is built of rough-cut granite quarried locally, with a gabled roof, two 20th-century gabled dormers on the north front, and a main entrance topped by a multilight transom window flanked by two sash windows.

The house's construction date is uncertain; its locally quarried granite was cut using a method that fell out of common use around 1750, distinct from the technique used for an 1830 foundation on the island. The earliest surviving real estate transactions involving Mosquito Island date to 1785, and the island's early history is poorly documented. The house was listed on the National Register of Historic Places in 1983 and restored after John Malone bought the island in 1995.

The house is named for Mosquito Island, the roughly 220-acre island it stands on about 2 miles south of Martinsville. The island has been private property since 1995, when John Malone, a billionaire businessman and philanthropist with large landholdings in Maine, bought it and had the house restored.

Mosquito Island is private property, owned since 1995 by John Malone, so the house and grounds are not open to visitors. The house stands in a clearing on the island's northwestern shore, about 2 miles (3.2 km) south of Martinsville and east of Marshall Point. It can only be seen from the water, from a boat in the Gulf of Maine.

The granite blocks were extracted using quarrying methods that gradually fell out of practice after 1750, making this house particularly notable. These hand-driven techniques allowed builders to create precisely fitted walls without modern machinery.