Stephania tetrandra is a herbaceous perennial vine of the family Menispermaceae native to China and Taiwan.

Stephania tetrandra occurs in shrublands at village margins, open fields, and roadsides in South Central and East China in Anhui, Fujian, Guangdong, Guangxi, Hainan, Hubei, Hunan, Jiangxi, and Zhejiang provinces, and in Taiwan.

Fen fang ji is used in traditional Chinese medicine to dispel wind and dampness to relieve pain and to promote diuresis.

The root contains many isoquinoline alkaloids: tetrandrine (0.6-0.9%), fangchinoline (0.5%), cyclanoline (0.1%) and dimethyltetrandrine iodide (muscle relaxant).

Notable among these is guang fang ji (Chinese: 廣防己; pinyin: guǎng fáng jǐ), Aristolochia fanchi, whose main toxic component is aristolochic acid, a potent carcinogen and nephrotoxin.