Yanjin County (simplified Chinese: 盐津县; traditional Chinese: 鹽津縣; pinyin: Yánjīn Xiàn) is located in the northeast of Yunnan Province, China, bordering Sichuan Province to the north and east. It is under the administration of the prefecture-level city of Zhaotong.

Situated on the banks of the narrow Heng River valley, a tributary of the Yangtze, Yanjing city has been referred to as the "World's Narrowest City." The buildings of the city are situated on tall pillars, which is a preemptive measure toward water-level rise during periods of heavy flooding. Videos of the city routinely go viral because of its uniqueness and the surrounding natural beauty, attracting much attention to the city.