The Common Merganser, (Goosander in Europe), Mergus merganser, is a large sized duck, which is distributed over Europe, North Asia and North America. It is most common on lakes and rivers. Its nests can be found in treeholes.

Males and females are easily distinguished, since the male merganser has a dark green head, while the head of the female is reddish-brown. The Common Merganser is 70 cm long with a 78-94 cm wingspan.

These large fish-eaters have serrated edges to their bills to help them grip their prey. Along with the Smew and the other Mergansers, they are therefore often known as "sawbills". They also eat mussels and shrimps; young birds mainly eat aquatic insects.

North American birds migrate south in small groups to the United States wherever ice free conditions exist on ponds, lakes and rivers; on the west coast, some birds are permanent residents.

Scandinavian and Russian birds also migrate southwards, but western European birds are largely resident.

The Common Merganser is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.