Chilli peppers (Capsicum spp.) are among the most economically valuable spice crops globally, valued for their pungency, vibrant colour, flavour, and functional bioactive compounds. This chapter provides a detailed overview of the major domesticated Capsicum species cultivated for commercial purposes, including Capsicum annuum L., Capsicum chinense Jacq., Capsicum frutescens L., Capsicum baccatum L. var. pendulum, and Capsicum pubescens Ruiz & Pav. Each species is described for botanical and morphological characteristics, geographic origin and domestication history. The discussion also extends to emerging and niche chilli varieties that are gaining attention for their unique sensory attributes or commercial potential. Furthermore, the chapter highlights key industrial applications of the chilli peppers, such as in the production of paprika, sauces, pickles, oleoresins, and their incorporation as functional or branding ingredients in processed foods and nutraceutical products. This comprehensive review underscores the expanding significance and versatility of chilli peppers across both traditional and modern markets.