Citrus fruits have garnered increasing attention owing to their prominent position in commerce, and valuable essential oils can be extracted from the by-products of citrus fruit processing. Citrus fruit essential oils mainly consist of monoterpenes, sesquiterpenes, and their oxygenated derivatives, along with other components that confer a variety of biological activities, including antibacterial, anti-inflammatory, antioxidant, and anti-anxiety properties. The essential oils that are extracted from citrus fruits thus possess broad prospects for application in the food, healthcare, and cosmetics industries. This paper provides an overview of the major components, key biological activities, mechanisms of action, and safety of essential oils extracted from citrus fruits such as sweet orange (Citrus sinensis), mandarin (Citrus reticulata), and lemon (Citrus limon), with the aim of providing a scientific reference for the practical application of such oils.