Rivers of Yambol Province

The Tundzha ( ; ; Tonsus in antiquity) is a river in southeastern Bulgaria and northwesternmost Turkey, a left tributary of the Maritsa. With a length of 390 km, of which 350 km are in Bulgaria, it is Maritsa's longest tributary, though in terms of discharge it is second after the Arda. Tundzha Glacier on Livingston Island in the South Shetland Islands, Antarctica is named after Tundzha River.

The Mochuritsa () is a river in southern Bulgaria, a left tributary of the river Tundzha of the Maritsa drainage, with a length of 86 km. It is the largest tributary of the Tundzha.

The Kalnitsa () is a 72 km long river in southern Bulgaria, a right tributary of the river Sinapovska reka, itself a left tributary of the Tundzha of the Maritsa drainage. It is the largest tributary of the Sinapovska reka and is longer than the latter.