Tongdao (the full name: "Tongdao Dong Autonomous County", simplified Chinese: 通道侗族自治县; traditional Chinese: 通道侗族自治縣; pinyin: Tōngdào Dòngzú Zìzhìxiàn; usually referred to as "Tongdao County", simplified Chinese: 通道县; traditional Chinese: 通道縣; pinyin: Tōngdào Xiàn) is an autonomous county of Dong people in Hunan Province, China, it is under the administration of the prefecture-level city of Huaihua.

Tongdao is also the 5th least-populous county of the province (after Shaoshan, Guzhang, Shuangpai and Yanling).

Located on the south western corner of Hunan province, Tongdao borders Guizhou to the west and Guangxi to the south.

The county lies in the southernmost part of Huaihua, it is the least populous and least densely populated county-level division of Huaihua.

The county covers 2,239 km2 (864 sq mi), as of 2015, it has a census registered population of 242,100 and a permanent resident population of 212,300.