Avenanthramides are a distinct class of hydroxycinnamic acid amides predominantly found in oats. Chemically, they are hydroxycinnamoyl anthranilates formed by the conjugation of an anthranilic acid derivative with a hydroxycinnamic acid, a structure that confers characteristic phenolic and aromatic functionalities underlying their bioactivity. In plants, avenanthramides act as phytoalexins and contribute to defense responses, including pathogen resistance and tolerance to abiotic stress. In humans, they exhibit a broad spectrum of protective effects, including anti-inflammatory, anti-oxidative, anti-proliferative, anti-fibrotic, anti-genotoxic, anti-atherogenic, and anti-irritant activities, highlighting their relevance as bioactive dietary components. Several natural variants have been identified, with nine major forms designated avn A–H and K [360].