Fa'side Castle (Faside Estate) has previously been known as Fawside, Falside, Ffauside, Fauxside, or Fawsyde and is a 15th-century keep located in East Lothian in Scotland. The castle is approximately 2 miles (3 kilometres) southwest of Tranent, and 2 mi (3 km) southeast of Musselburgh. The building was restored in the 1980s and is now protected as a category B listed building.

The restoration of castles and tower houses in Scotland, generally by private individuals and families, has been taking place for over a century and is of major significance in the field of historic buildings in the country, sometimes a subject of controversy.