Ambrysus amargosus is a rare species of insect in the family Naucoridae, the creeping water bugs. It is known by the common name Ash Meadows naucorid. It is endemic to Ash Meadows in Nye County, Nevada, where it is now restricted to one system of springs. It is a federally listed threatened species of the United States. Little is known about the insect's life history, but closely related insects feed on insect larvae and lay eggs underwater in the substrate.