Stora Nassa, Nature reserve in Stockholm archipelago, Sweden.

Stora Nassa is an island group in Nassa skärgård, Värmdö Municipality, about 15 km east of Möja. Its main island, Stora Bonden, measures roughly 950 m north-south and 450 m at its widest; the longest island, Jungfruskär, just north of it, runs about 1,100 m north-south and 350 m wide. The islands are high and rocky, and the group extends about 6 km north-south and 3 km east-west.

In the Middle Ages Stora Nassa was a crown fishing harbour where fishermen stayed temporarily during the herring season. The main island, Stora Bonden, gained permanent residents in the 18th century, at most six families living by fishing and seabird hunting. The last permanent inhabitant, "Antegubben" Anders Österberg, died in 1930 at 96; his life is told in Den siste skärkarlen by his grandson Harry Sjöberg.

Stora Nassa was a crown fishing harbour in the Middle Ages, when fishermen stayed temporarily during the herring season. The last permanent resident was "Antegubben" Anders Österberg, who died in 1930 at 96; his life is told in the book Den siste skärkarlen by his grandson Harry Sjöberg.

Access to this reserve requires a private boat, with camping allowed only on Beckskaret and Stor Sprangskaret islands. Visitors should check weather conditions before heading out and plan navigation carefully given the complex island layout.

Among the mammals on the islands is a feral population descended from a cross between mouflon and Gotland sheep, a hybrid that grazes the rocky islets. The reserve covers about 4.1 square kilometres, and its highest point rises only 21 metres above the sea.