Opaka (Bulgarian: Опака) is a town in the district of Turgovishte in northeast Bulgaria. As of December 2009, the town had a population of 2,873 and covers an area of 57 km². It is 70 km south of the city of Rousse on the border with Romania and 250 km northeast of the Bulgarian capital, Sofia. Archeologists have found evidence of Thracian, Roman and Slavonic settlements in the area. Near the village of Krepcha, a stone monastery is the site of the oldest known Old Bulgarian Cyrillic inscription, dated from around 920 CE. A 2nd century Thracian tumulus containing various artifacts, including six leaves of a golden wreath and bronze figurines, was excavated in 2011.

The associated Opaka municipality includes the town and five villages, Garchinovo, Golyamo Gradishte, Gorsko Ablanovo, Krepcha and Lyublen.

Opaka Rocks off Robert Island, South Shetland Islands are named after Opaka.

Coordinates: 43°27′N 26°10′E / 43.45°N 26.167°E / 43.45; 26.167