Tvarditsa Valley (Bulgarian: Твърдишка котловина) is situated in central Bulgaria.

The average altitude varies between 200 m and 250 m.[1] The Tvarditsa Valley is inclined in southern direction.

The slopes are built up of granite, Paleogene clays, gneiss, sandstone and conglomerates and are subject to active erosion.

From west to east between Nikolaevo and Bliznets passes a 20 km stretch of the first class I-6 road Gyueshevo–Sofia–Karlovo–Burgas.

The main industry is textiles, based in Tvarditsa, with export markets in Sweden, France, Canada, Greece and Serbia.