The Topolovets (Bulgarian: Тополовец) is a river in northwestern Bulgaria, a right tributary of the Danube.

[1] The river takes its source under the name Mostishte at an altitude of 404 m about a kilometer east of the summit of Vrashka Chuka (693 m) in the northwesternmost part of the Balkan Mountains and flows in the western Danubian Plain.

Downstream of the village it turns southeast, enters the Vidin Plain and flows into the Danube at an altitude of 33 m.[1] Its drainage basin covers a territory of 583 km2 and is situated between the basins of the rivers Timok to the west and northwest, the Voynishka reka to the south, and several small rivers flowing into the Danube to the north and northeast.

The river has predominantly snow–rain feed with high water during the snowmelt in early spring.

Along its left bank in the middle course runs a 10 km stretch of the third class III-121 road Inovo–Boynitsa–Kula.