Oreodytes sanmarkii is a species of predaceous diving beetle in the family Dytiscidae. It has a holarctic distribution, found in aquatic habitats in Europe, northern Asia (excluding China), and North America. It has an affinity toward low-velocity currents and pebbly microhabitat substrates. It was described by Finnish entomologist Carl Reinhold Sahlberg in 1826.
There are two named subspecies of Oreodytes: