The Hallingdalselva (also Hallingdalselve - official spelling) is a river in the Norwegian Fylke Buskerud. The river has a length of 220 km (total length with headwaters and Snarumselva ) and a catchment area of 4587 km ². The Hallingdal is the main river in the river system Hallingdalsvassdraget.
The river has its origin in the Hardangervidda. The Usta from the lake and the Ustevatn Holselva from the lake Strandavatnet unite west of the lake beach fjords to the Hallingdal. These first flows through the beach fjords, then flows in a northeasterly direction towards Gol, then turns to the southeast and flows through the Hallingdal Valley. South of the river has some Nesbyen its widest passages. The Brommafjorden is one of those sections of the river. The Hallingdalselva flows into the lake at Krøderen Gulsvik. After discharge from the Krøderen the river is then called Snarumselva. Finally, the flow associated with the Drammen River, only to culminate in Drammen in the Skagerrak.
A number of rivers flow into the Hallingdal. These include the Votna, Lya, Hemsil, Todøla and Rukkedøla. Above Gol is the maximum gradient of the river. The Municipality of Oslo where he runs several hydroelectric plants.