Sundsby, Historic manor house in Tjörn Municipality, Sweden.

Sundsby Säteri stands as a well-preserved 18th-century manor house complex surrounded by wooded hills and natural bays on the island of Mjörn in Bohuslän.

Originally mentioned in Bishop Eystein's Land Book from 1388, the estate was rebuilt around 1763 after fire destroyed the original medieval structures in 1720.

The manor's name comes from the estate that Laurits Olofsson Green took over in the late 16th century; his descendant Margareta Huitfeldt ran it alone after her husband Thomas Dyre died in 1651. An exhibition in the buildings covers her life, and the side buildings hold a café, restaurant, shop and bakery.

The buildings and the park around them are private ground, while the surrounding area is a nature reserve managed by the Västkuststiftelsen and part of Natura 2000. Several hiking trails run through the surroundings; the white-and-blue marked trail passes Springareeken, a few hundred metres from the manor. The manor has been a listed building since 30 March 1981.

A few hundred metres from the manor, along the white-and-blue marked trail, stands Springareeken, an oak believed to be 900 years old and counted among the world's oldest oaks. The surrounding area is a nature reserve within the EU Natura 2000 network, managed by the Västkuststiftelsen.