Viidumäe Nature Reserve (Estonian: Viidumäe looduskaitseala) is a nature reserve situated on Saaremaa in western Estonia, in Saare County.

The nature reserve is located in the west of Saaremaa, on the oldest and highest lying part of the island.

[2] As regards to the flora, the nature reserve is home to the Rhinanthus osiliensis, a species of rattle which can only be found on Saaremaa and Gotland islands in the Baltic Sea.

The bird life is rich with species like black woodpecker, Eurasian pygmy owl, black stork and white-tailed eagle as typical representatives.

Mammals such as elk and wild boar are frequent in the area.