Wensu County, also known as Onsu County, is a county located in the Xinjiang Uygur Autonomous Region of China. It falls under the administration of Aksu Prefecture and covers a total area of 14,309 km2 (5,525 sq mi).
The region is situated along the northwestern border of the prefecture, where it shares a boundary with Kyrgyzstan's Issyk-Kul Region to the northwest.