The Trgoviški Timok (, Timok of Trgovište) is a river in Serbia, also known as Korenatac (Cyrillic: Коренатац) or Strma river ( / Strma reka, Steep river). It starts on the western slopes of the Balkan Mountains (Stara Planina mountains), right under the highest peak of the mountain in Serbia, Midžor, less than a kilometer from the Bulgarian border. The river runs to the east, receiving three smaller streams from the other peaks of Balkan mountain range with colorful names (Babin Zub and Tri Uši, Cyrillic: Бабин Зуб and Три Уши, Oldwife's Tooth and Three Ears). The river passes through the villages of Balta Berilovac, Vrtovac and Inovo. On this reach it receives the Debelička and Ćuštička rivers from the left and the Golaška and Inovska rivers from the right. At the village of Kalna, it is joined by the Stanjanska River, flowing down the northern slopes of the Jadovnik mountain, turns to the north and becomes known as the Trgoviški Timok.