The Fondillón is a wine made from overripe grapes of the Monastrell variety, which is characterized by a high alcohol content and a minimum barrel ageing of 10 years. The objective of this study was to analyze the Fondillón volatile composition, key aroma-active compounds, sensory profile and phenolic composition. Fifty-four volatile compounds were identified, quantified and classified as alcohols, esters, acids, aldehydes, lactones, phenols, hydrocarbons and ketone. From these compounds, 22 aroma-active compounds were identified, with phenylethyl alcohol, diethyl succinate and ethyl lactate having the highest flavor dilution factor. The Fondillón wines were characterized by having high intensity of alcohol, fruity and toasted odor and flavor notes, and long aftertaste. Besides, 25 phenolic compounds were also identified and quantified; the phenolic acids (gallic, protocatechuic and syringic acids) were the predominant phenolic compounds.