灰雁（学名：Anser anser），又名大雁、沙鹅、灰腰雁、红嘴雁、沙雁、黄嘴灰雁，为雁属模式种。

灰雁栖息于湖泊、河滩水域地带。他们经常选择水生植物密布的环境藏身，有时也在开阔的湖面游荡。憩息时常有一些灰雁放哨警戒。早展、夜间或黄昏出来觅食。

The greylag goose (Anser anser) is a bird in the waterfowl family Anatidae. It has mottled and barred grey and white plumage and an orange beak and legs. A large bird, it measures between 74 and 91 centimetres (29 and 36 in) in length, with an average weight of 3.3 kilograms (7.3 lb). Its distribution is widespread, with birds from the north of its range in Europe and Asia migrating southwards to spend the winter in warmer places. It is the type species of the genus Anser and is the ancestor of one type of domestic goose, having been domesticated at least as early as 1360 BC. The genus name is from anser, the Latin for "goose".