|Length||135.6 km (84.3 mi)|
|Basin size||1,780 km2 (690 sq mi)|
|Progression||Maritsa→ Aegean Sea|
The Topolnitsa (Bulgarian: Тополница [toˈpɔɫnit͡ʃɐ]) is a river in southern Bulgaria, an important left tributary of the Maritsa. It takes its source from Bich Peak in Sredna Gora close to Koprivshtitsa; it is known as the Shirineyska in its upper course. Its average discharge is 55 m3/s and it is 135.6 kilometres (84.3 mi) long; its drainage basin covers 1,780 square kilometres (690 sq mi). The Topolnitsa flows into the Maritsa near Pazardzhik after making a large turn under Trakiya motorway. The Topolnitsa Reservoir has a maximum volume of 120,000,000 cubic metres (4.2×109 cu ft) and serves the area around Pazardzhik. Among the Topolnitsa's tributaries are the Mativir and the Bunovo River. The river's name is derived from the Bulgarian word топола, topola ("poplar").
- "Тополница". Българска енциклопедия А-Я (in Bulgarian). БАН, Труд, Сирма. 2002. ISBN 954-8104-08-3. OCLC 163361648.