The Rupel is a tidal river in northern Belgium, right tributary of the Scheldt. It is about 12 kilometres (7 mi) long. It flows through the Belgian province of Antwerp. It is formed by the confluence of the rivers Dijle and Nete, in Rumst. It flows into the Scheldt at Rupelmonde. Towns along the Rupel are Rumst, Boom and Niel. The Rupel is navigable, and forms part of the waterway to Brussels.
The Rupelian Age of the Oligocene Epoch in the geological time scale is named after this river.