Jianhu is a county under the administration of Yancheng, a prefecture-level city in Jiangsu province, China. It lies in the northern part of the province, bordering the prefecture-level cities of Huai'an and Yangzhou to the west.
Its position places it within the coastal province of Jiangsu, a region of eastern China along the Yellow Sea. The county's administrative seat and surrounding towns form part of Yancheng's wider jurisdiction.
Note that the subject requested here is Jianhu in Jiangsu province. A separate and unrelated place, Jianhu County in Zhejiang province, is sometimes confused with it, but the two are distinct and located in different provinces.