Rhynchomesostoma rostratum is a species of rhabdocoel flatworms in the family Typhloplanidae.
The animal is 1.5 to 3.5 mm long and transparent. The anterior end is retractable.
It was described by Otto Friedrich Müller in 1774 as Fasciola rostrata.
The species has been recorded in Europe, India, Kenya, Siberia, and the US.
It preys on oligochaetes, cladocerans, copepods, other microturbellarians, and mosquito larvae and other aquatic insects. It is preyed upon by the flatworm Phaenocora unipunctata.