Hu Xiansu or Hu Hsien-Hsu (simplified Chinese: 胡先骕; traditional Chinese: 胡先驌; pinyin: Hú Xiānsù, 24 May 1894 – 16 July 1968), was a Chinese botanist and an influential traditional scholar of his time. He was a founder of plant taxonomy in China and a pioneer of modern botany research in the country.
Hu Xiansu studied preparatory course at Imperial University of Peking in 1909. In 1912 after the 1911 Revolution he went to America, and graduated from University of California, Berkeley in 1916. In 1918, he became a faculty member of National Nanking Higher Normal School and then National Southeastern University (later renamed National Central University and Nanking University). He went to America again in 1923 and received a doctor's degree from Harvard University in 1925. His wife died in Nanking in 1926, then he resigned from Department of Biology of Southeastern University and became a full-time research fellow at Institute of Biology of China Science Society. He cofounded Fan Memorial Institute of Biology in Peiping (Beijing) in 1928. He founded Lushan Botanical Garden in 1934 and Yunnan Institute of Agriculture and Forest (later renamed Kunming Institute of Botany, Chinese Academy of Sciences) in 1938.