The Bolgarchay (Bolqar çay in Azerbaijani, بالهارود Bālhārūd in Persian), is a river, which forms part of the Azerbaijan–Iran border. It is 134 km (83 mi) long, and has a drainage basin of 2,170 km (840 sq mi).

The Balharud rises from Oujarud Mountains near Siya, a small village on the Iranian-Azerbaijan border. It is joined by its tributaries including the Salala in Azadli, the Hamzakhanli in Tapabashi, the Germi in Hadibeyli and the Barzand in Beygbaghili; all flowing from the Iranian side of its catchment area. It flows along the Iranian-Azerbaijani border, and then along a corridor that connects Turkey to Azerbaijan's Nakhchivan exclave. It then again flows along the Iranian-Azerbaijani border and leaves Iran at Bilesavar to enter Azerbaijan proper. The Balharud pours into Mahmud-Chaleh Lake.

39°25′03″N 48°41′03″E / 39.4175°N 48.6842°E / 39.4175; 48.6842