Tundzha Municipality (Bulgarian: община Тунджа) is a municipality of Yambol Province, southeastern Bulgaria.

The municipality has an area of 1,218.86 square kilometres, making it the second-largest by area in the country after the Capital Municipality (i.e. the city of Sofia).

The following villages are part of Tundzha Municipality: A notable native is Ivan Atanasov, the father of John Vincent Atanasoff (1903–1995), Bulgarian American physicist and inventor of the first automatic electronic digital computer.

The Bezmer Air Base, one of the joint US-Bulgarian military bases, is also located in the municipality, near the villages of Bezmer and Bolyarsko.

According to the latest Bulgarian census of 2011, the religious composition, among those who answered the optional question on religious identification, was the following: