The Sutla (Croatian) or Sotla (Slovene) is a river flowing through Slovenia and Croatia, mostly forming their border.

[2] The Sutla flows through the following municipalities: The hydrological parameters of the Sutla are regularly monitored in Croatia at Zelenjak.

[3] The division of the Sutla/Sotla basin area between Croatia and Slovenia is inconsistent in sources; Croatian sources claim either 343 km2 (132 sq mi)[4] or 455 km2 (176 sq mi),[5] while Slovenian sources claim either 477 km2 (184 sq mi)[6] or 451 km2 (174 sq mi).

It covers 206 km2 (80 sq mi) of the landscape of the Kozje Hills (Kozjansko hribovje), including wetlands along the Sotla.

[7] The earliest known mention of Sutla was in 1028, as Zontla.