Underwood's water mouse

{{Short description|Species of rodent}}

{{speciesbox

| name = Underwood's water mouse

| status = LC | status_system = IUCN3.1

| status_ref = {{cite iucn |author=Naylor, L. |author2=Roach, N. |date=2016 |title=Rheomys underwoodi |volume=2016 |page=e.T19487A22354257 |doi=10.2305/IUCN.UK.2016-2.RLTS.T19487A22354257.en |access-date=15 November 2021}}

| genus = Rheomys

| species = underwoodi

| authority = Thomas, 1906

| synonyms =

}}

Underwood's water mouse (Rheomys underwoodi) is a species of rodent in the family Cricetidae.{{MSW3 Muroidea | id = 13000882 | page = 1167}} It is found in Costa Rican and western Panamanian cloud forest at altitudes from 1500 to 2000 m. This mouse lives near streams in highland forests and is semiaquatic; its carnivorous diet includes invertebrates. Although its range is small, it includes a number of protected areas, and the population appears to be sizable; the IUCN therefore rates the conservation status of the species as "least concern".