Citrus fruits have long been popular around the world and are a good source of Vitamin C. Citrus also contains many other functional bioactive phytochemicals including triterpenic acids, flavonoids, cerebrosides, amino acids, phenolic acids, mineral constituents, and polysaccharides, which are beneficial to human health. This book provides a general summary of current research results in the citrus fruits and citrus foods, extensively reviewing functional bioactive phytochemicals in citrus fruits such as polysaccharide, terpenes, polyphenols, carotenoids, and limonoids.