View of the Timok at Baley, Bulgaria
|- left||Crni Timok|
|- right||Beli Timok|
|City||Serbia: Zaječar, Brusnik
Bulgaria: Bregovo, Baley
|- location||Junction of the Beli Timok and the Crni Timok, Serbia|
|- location||near Bregovo, Serbia, Bulgaria|
|- average||24 m3/s (848 cu ft/s)|
It is a very branchy system of many shorter rivers, a large number of them having the same name (Timok), only clarified with adjectives. From the farthest source in the system, that of the Svrljiški Timok, until its confluence into the Danube (as Veliki Timok), the Timok is 203 km long. The river flows through Serbia and for the last 15 km forms the border between Serbia and Bulgaria. The area of the river basin is 4,630 km². The Timok Valley is known for the most important Romanian-speaking population in Eastern Serbia.
Drainage system 
The Timok, also named Veliki Timok to distinguish it from its tributaries, is formed by the confluence of the rivers Beli Timok ("White Timok") and Crni Timok ("Black Timok") at Zaječar. The Beli Timok is formed by the confluence of the rivers Svrljiški Timok ("Svrljig Timok") and Trgoviški Timok ("Trgovište Timok") at Knjaževac.
Tributaries of the Timok are Duboki Dol, Beslarica, Golami Dol, Kijevska, Bračevicka, Studena Voda, Pivnica and Eleshchev from the right, and Lipovička River, Crna reka, Jelašnička reka, Salaška reka, Ogašu Taba, Brusnički potok, Urovički potok, Plandište and Sikolska river from the left.
The Timok turns north-west after its formation at Zaječar, running next to the villages of Vražogrnac, Trnavac, Čokonjar, and Brusnik. Passing between the last two it leaves Timočka Krajina and enters Negotinska Krajina.
In the lower course the Timok has no major settlements on the Serbian side (though flowing only 7 km from Negotin). Some 15 km before it empties into the Danube as its right tributary, the Timok becomes a border river, passing next to the Bulgarian town of Bregovo and the Bulgarian village of Baley. The river's mouth represents the northernmost point of Bulgaria, and is only 28 m above sea level, which makes it the lowest point of Serbia. The average discharge is 24 m³/s, but it can grow to 40 m³/s, and the Timok is part of the Black Sea drainage basin. The main (right) tributaries in this section are Crna reka, Salaška reka, Sikolska reka and Čubarska reka (Cyrillic: Црна река, Салашка река, Сиколска река and Чубарска река).
Economy and ecology 
At Čokonjar, the Sokolovica power plant was constructed in 1947-1951. Opportunities for higher electricity production are not used.
- Mala Prosvetina Enciklopedija, Third edition (1985); Prosveta; ISBN 86-07-00001-2
- Jovan Đ. Marković (1990): Enciklopedijski geografski leksikon Jugoslavije; Svjetlost-Sarajevo; ISBN 86-01-02651-6
- The Cambridge Ancient History Vol. 10, John Boardman, p 579, 1996, ISBN 978-0-521-85073-5