Plinius is a prominent lunar impact crater on the border between Mare Serenitatis to the north and Mare Tranquilitatis to the south. Its diameter is 41 km. The crater is named after the Roman natural scientist and author Pliny the Elder. To the south-southeast of Plinius is the crater Ross, and to the northeast is Dawes. Just to the north is a system of rilles named the Rimae Plinius and touching it is the Brackett crater which is more than a crater diameter north. At the northwest edge of the rille is the Promontorium Archerusia, a cape off the western rim that encloses the Mare Serenitatis.