Carotenoids are yellow, orange, or red pigments, also known as accessory pigments, found in bacteria, fungi, cyanobacteria, algae, and higher plant parts such as flowers, fruits, and storage roots. They are classified into two groups: carotenes and xanthophylls. Carotenoids are synthesized through two distinct pathways—the mevalonate (MVA) pathway and the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway. Both pathways converge to produce isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP), which are essential precursors for various isoprenoids, including carotenoids. Carotenoids can be extracted from plant materials or produced through bioprocessing technologies using microorganisms. The fermentation process for microbial carotenoid biosynthesis requires meticulous control of nutritional and processing parameters and involves both upstream and downstream steps to ensure efficient extraction and recovery of microbial carotenoids. Several strategies have been employed to reduce costs and enhance yields, such as metabolic engineering and recombinant DNA technology. Among the commercially significant carotenoids for human health and medicine are astaxanthin, β-carotene, canthaxanthin, lutein, lycopene, and zeaxanthin. Carotenoids possess various biological properties, including providing coloration to plants and animals, acting as photoprotective agents, alleviating stress, functioning as hormones in plants and animals, serving as precursors to vitamin A, and contributing to the prevention of human diseases such as cancer and neurodegenerative disorders. The applications of carotenoids extend to their use as food colorants, animal feed supplements for livestock and poultry, and health promotion in humans in the form of supplements in the pharmaceutical and nutraceutical industries.