The Blatnica Valley () is a karst valley in the Greater Fatra Range in Slovakia. It is 8 km long.
It is accessible from the village of Blatnica along a dirt road. Most of the valley is densely forested, in places with views at the surrounding limestone and dolomite strata. The best-known part of the valley is the rock window at its lower part. Ostrá and Drieà Âok mountains can be climbed from the valley bottom.