Hu Xiansu or Hu Hsen-Hsu was a Chinese botanist and scholar. He was the founder of plant taxonomy in China and a pioneer of modern botany and paleobotany research in the country. One of his most notable achievements as a botanist was the discovery of the living fossil Metasequoia glyptostroboides in the 1940s, which previously thought to have been extinct for over 150 million years. This has been considered one of the most important botanical discoveries of the 20th century.

Metasequoia glyptostroboides, the dawn redwood, is a fast-growing, endangered deciduous conifer. It is the sole living species of the genus Metasequoia, one of three genera in the subfamily Sequoioideae of the family Cupressaceae. It now survives in the wild only in wet lower slopes and montane river and stream valleys in the border region of Hubei and Hunan provinces and Chongqing municipality in south-central China, notably in Lichuan county in Hubei. Although the shortest of the redwoods, it can grow to 167 ft (51 m) in height.