Pseudophilautus semiruber is a species of frog in the family Rhacophoridae that is endemic to Sri Lanka. Pseudophilautus semiruber is one of the smallest frog species in Sri Lanka and it is also one of the world's smallest frogs, measuring less than 15 mm in snout-to-vent length (diminutive species). A single specimen of this species was first discovered in 1911 and described by Annandale in 1913, referring to it as Ixalus semiruber. For the next 95 years since 1913, this species was not again seen alive, and the type specimen on which the original description was made, was confirmed to be lost from a Museum collection by 2001.