Sandemar Nature Reserve, Nature reserve in Stockholm County, Sweden.

Sandemar Nature Reserve covers 390 hectares, of which 227 are land, east and west of Sandemar Castle, whose grounds are excluded. It runs about 3.5 km along the inner Stockholm archipelago southwest of Dalarö, with coastal meadows, shallow bays and a rich fen in the east.

The area was designated as a protected nature reserve in 1997, safeguarding landscapes that have been part of a manorial estate for centuries. This long history is reflected in the natural structures and habitats that remain today.

The reserve protects traditional Swedish coastal meadow environments that shape the local landscape character. Walking through these spaces, visitors experience the natural settings that have defined this region for generations.

The reserve stretches about 3.5 km along the inner Stockholm archipelago southwest of Dalarö, with a bird-watching tower near the water. The coastal meadows and Svärdsnäsviken are best visited in spring and autumn, when waders and migrating birds rest there. The reserve is reached by commuter train to Handen station.

The eastern fen is mown regularly to keep its rich fen flora, which includes the carnivorous common butterwort and the fen orchid. The reserve is also one of the few places in the Stockholm area where the rosefinch breeds in summer.