The Ipeľ (Slovak; ]) or Ipoly (Hungarian) (German: Eipel, archaic Slovak: Jupoľ, Latin: Bolia) is a long river in Slovakia and Hungary, a tributary of the Danube River. Its source is in central Slovakia in the Slovak Ore Mountains. It flows south to the Hungarian border, and then southwest, west, and again south along the border until it flows into the Danube near Szob.