The Vlahina reka (Bulgarian: Влахина река) is a river in south-western Bulgaria, a left tributary of the Struma.

[1][2] The river is 27 km long and drains part of the western sections of the Pirin mountain range.

It flows westwards in a glacial valley; after the Gredaro ridge it turns southwest in a heavily forested in region.

The average annual flow at the confluence with the Struma is 1.69 m3/s,[1] although during snowmelt the amount of water may increase tenfold to 14.6 m3/s.

The only settlement along the river is Vlahi in Kresna Municipality, Blagoevgrad Province, from which its name originated.