Medicinal aromatic plants are very important for human health. Due to the polyphenolic and phytochemical components they contain, they have antioxidant, antibacterial, anticancer, antiviral and anti-inflammatory properties. For this reason, it is the subject of scientific studies. Allium species are important medicinal and aromatic plants that include the commonly known onion and garlic species. There are many different species and the different biological activities of these species are determined by scientific studies. For this reason, in this chapter, the ethnobotanical characteristics and biological activities of important Allium species with current scientific studies are compiled. It is stated that some of these species have anticancer properties and their consumption will be beneficial for health.