Moksha is a river in central Russia, a right tributary of the Oka. It flows through Penza Oblast, Nizhny Novgorod Oblast, Ryazan Oblast and the Republic of Mordovia, and joins the Oka near Pyatnitsky Yar, near the city of Kasimov.

The Oka is a river in central Russia, the largest right tributary of the Volga. It flows through the regions of Oryol, Tula, Kaluga, Moscow, Ryazan, Vladimir and Nizhny Novgorod and is navigable over a large part of its total length, as far upstream as the town of Kaluga. Its length is 1,500 km (930 mi) and its catchment area 245,000 km2 (95,000 sq mi). The Russian capital Moscow sits on one of the Oka's tributaries—the Moskva.