Limonoids are one of the most health-benefiting bioactive components of citrus fruits owing to their versatile health-promoting and disease-preventing properties. Citrus limonoids were considered as the culprits causing delayed bitterness of the juices at room temperatures lowering the juice quality. Limonoids are highly oxygenated and modified triterpenes classified as tetranortriterpenoids. The term ‘limonoid’ is derived from limonin, the first limonoid component identified as the bitter component of citrus seeds. Several other limonoid compounds such as obacunone, nomilin, obacunoic acid, isolimonic acid, deacetylnomilin, ichigan, isoobacunoic, and dictomnolide were also identified. Limonin and nomilin are the predominant limonoids of citrus fruit. Limonoids are grouped into aglycones and glucosides. Aglycones are bitter limonoid compounds in the peels of citrus fruits, while glucosides are tasteless components. Both aglycones and glucosides are present in citrus seeds, but fruit tissue contains only glucosides. More than 50 limonoid aglycones and glucosides have been identified from various Citrus species. Evidence from several in vivo, in vitro, and animal studies suggests that limonoids have anticancer properties and showed potent cytotoxic activities