Stream capture is a geological event , geological phenomenon or hydrological phenomenon which occurs when a stream from a neighboring drainage erodes through the divide between two streams and "captures" another stream which then is diverted from its former bed and now flows down the bed of the capturing stream.

One instance of a stream capture is the capture of the Rio Grande which before capture flowed into a closed basin , Lake Cabeza de Baca , but after capture flowed into the Gulf of Mexico.

A stream capturing currently developing in Germany is the Donauversickerung, where a big portion of the upper parts of the Danube river sink into the limestone bedrock, and resurface in the Aachtopf spring, a tributary to the Rhine river.