The Blue-headed Wagtail (Motacilla flava), also known by a number of other names such as Yellow Wagtail is a small passerine in the wagtail family Motacillidae, which also includes the pipits and longclaws.

This species breeds in much of temperate Europe and Asia and has a foothold in North America in Alaska. It is resident in the milder parts of its range, such as western Europe, but northern and eastern populations migrate to Africa and south Asia. The Beringian population, Eastern Yellow Wagtail, winters further down the Pacific coast.

This is an insectivorous bird of open country near water, such as wet meadows. It nests in tussocks, laying 4-8 speckled eggs.

This is a slender 15-16 cm long bird, with the characteristic long, constantly wagging tail of its genus. It is the shortest tailed of the European wagtails. The breeding adult male is basically olive above and yellow below. In other plumages, the yellow may be diluted by white.

The heads of breeding males come in a variety of colours and patterns depending on subspecies.

This species' systematics and phylogeny is extremely confusing. Literally dozens of subspecies have been described at one time or another, and some 15-20 are currently considered valid depending on which author reviews them. In addition, the Citrine Wagtail forms a cryptic species complex with this bird (Voelker 2002); both taxa are paraphyletic in respect to each other.

Nominate Blue-headed Wagtail and Yellow Wagtail form a narrow hybrid zone in northern France. Birds from this zone vary in appearance, but one type, which resembles nominate Blue-headed Wagtail (except that the blue tones to the head are paler and more mauve and the white of the head is more extensive, particularly on the throat, ear-coverts, and supercilium) is colloquially referred to as Channel Wagtail.