The limestone leaf warbler (Phylloscopus calciatilis) is a species of warbler in the family Phylloscopidae. When this species was first seen, beginning in 1994, it was mistaken for the similar sulphur-breasted warbler. It is smaller than the sulphur-breasted warbler, and has more rounded wings. The plumage is almost identical, with comparisons showing only a slightly colder yellow below and a greyer tinge above. Although smaller, the bill is proportionally larger than that of the sulphur-breasted warbler. Accurate measurements are not available; the holotype has a wing length of 5.2 centimetres (2.0 in); the paratype a tail length of 3.7 centimetres (1.5 in) and a bill length of 1.39 centimetres (0.55 in). The species is known to occur in northern Vietnam and Laos, and potentially also occ