The Gansu leaf warbler (Phylloscopus kansuensis) is a small passerine bird known only from China. It belongs to the leaf warbler genus Phylloscopus within the family Phylloscopidae. It was formerly treated as a subspecies of Pallas's warbler (P. proregulus) but is now regarded as a separate species based on differences in voice and cytochrome-b gene sequences. The song is very different from Pallas's warbler and consists of a thin, high-pitched note followed by a series of accelerating notes and finally a trill.