Fållnäs, Manor house in Sorunda, Sweden

Fållnäs is a manor estate between Fållnäsviken and Himmerfjärden in Sorunda parish, Nynäshamn Municipality. Its six paired wing buildings stand along an east-west axis, built 1780-1807 to plans by Erik Palmstedt, with pink walls and white plaster bands. The palace-like main building he designed was never built; the southeast wing, marked by a pediment, served as the residence instead.

The property dates to 1291 when Magnus Johansson owned it and later gave it to Sko Monastery. This monastic connection influenced the estate's development and role in the region for centuries afterward.

Fållnäs takes its name from the old form Faldanes, recorded in 1291. Since 2007 an art gallery has run in one of the estate buildings, while the Toll family, owners since 1930, still farm and manage forest here. Many crofter's cottages around the manor survive and shape the surrounding farmland.

The estate lies between Fållnäsviken and Himmerfjärden in Sorunda parish, Nynäshamn Municipality. The buildings are private and used as rented homes, with an art gallery in one house since 2007; the grounds are working farmland and forest, so visits should be arranged with the management beforehand.

The site originally contained a medieval defensive tower with exceptionally thick walls, representing one of Sweden's largest kastal-type structures. Though no longer standing, its former presence reveals the strategic importance the location held in earlier times.