The Willow Warbler, Phylloscopus trochilus, is a very common and widespread leaf warbler which breeds throughout northern and temperate Europe and Asia.

It was described by Linnaeus in his Systema Naturae in 1758 under the genus Motacilla.

This "warbler" is strongly migratory and the majority of the population winters in sub-Saharan Africa. It is one of the first leaf warblers to return in the spring but is later than the Chiffchaff, Phylloscopus collybita.

This is a bird of open woodlands with trees and ground cover for nesting, including birch and willow uplands. The nest is built in close contact with the ground, often in low vegetation. Like most Old World warblers, this small passerine is insectivorous.

This is a typical leaf warbler in appearance, greenish brown above and off-white below. It is very similar to the Chiffchaff, but non-singing birds can be distinguished from that species by their paler legs, longer paler bill, more elegant shape and longer primary projection. Its song is a simple repetitive descending whistle.