Many eubacteria use aromatic molecules as a carbon and energy source, but only a few archaea have been reported to grow on aromatics. Degradation of aromatic hydrocarbons by aerobic bacteria is generally divided into an upper pathway, which produces dihydroxylated aromatic intermediates by the action of monooxygenases, and a lower pathway that processes these intermediates down to molecules that enter the citric acid cycle. Recently, analysis of the genome of the thermophilic archaeon Sulfolobus solfataricus revealed the existence of orfs coding for putative enzymes of the degradation pathway of aromatics, i.e., a cluster of orfs coding for the subunits of a hypothetical bacterial multicomponent monooxygenase (SsoMO), an orf coding for a catechol 2,3-dioxygenase (SsoC2,3O), and an orf coding for an enzyme of the lower pathway of the catechol metabolism. In this paper we report that S. solfataricus can efficiently grow on phenol as the sole source of carbon and energy. To our knowledge this is the first report of a thermophilic archaeon able to grow on an aromatic compound under aerobic conditions. Moreover, the cloning and heterologous expression and characterization of the thermophilic SsoC2,3O are reported.