茎基，是一种植物茎的变形，一般为木质，形态粗短，存活多年，生长在地下或地表，不进行光合作用。茎基有时为球块状，可储水；特别是旱生植物，茎基上可以长出枝叶。

A caudex (plural: caudices) of a plant is a stem, but the term is also used to mean a rootstock and particularly a basal stem structure from which new growth arises.

In the strict sense of the term, meaning a stem, "caudex" is most often used with plants that have a different stem morphology from the typical angiosperm dicotyledon stem: examples of this include palms, ferns, and cycads.