**Abstract**

Cotton is the most critical fiber crop and one of the top three oilseed crops in the world. One pronounced feature of cotton is that it is rich in secondary metabolites, mainly including terpenoids, flavonoids, and phenolic acids. These secondary metabolites have various ecological roles, such as defense and signal transmission. With the concept of plant secondary metabolites becoming more and more evident in the midtwentieth century, cotton secondary metabolites as natural phytoalexins were also established. Terpenoids are stored in pigment glands that are distributed almost all cotton plant surfaces or subsurfaces and defend cotton plants from chewing insects, pathogens, and other herbivores. Flavonoids are relevant to fiber quality and color and also play a role in mechanism in insect and pathogen resistance. Phenolic acids play a role in weed suppression and insect and pathogen resistance. There are several reviews on cotton secondary metabolites, and the most recent one was five years ago. They all focus on the metabolites themselves. None of them focus on applications in cotton production. This review started from browsing the abundant literature on cotton secondary metabolites, and then analyzing their potential application in cotton production. Finally, our recent findings were discussed in this chapter.

**Keywords:** cotton, terpenoid, flavonoid, phenolic acid, insect, pathogen, weed
