Denis O'Brien (born 19 April 1958) is an Irish billionaire businessman, and the founder and owner of Digicel. He was listed among the World's Top 200 Billionaires in 2015 and was Ireland's richest native-born citizen for a period of several years. His business interests have also extended to aircraft leasing (Aergo Capital), utilities support (Actavo), petroleum (Topaz Energy), football (a minority shareholder of Celtic F.C.), and healthcare (Beacon Hospital). As former chairman of the Esat Digifone consortium, O'Brien was questioned by the Moriarty Tribunal, which investigated the awarding of a mobile phone licence to Esat, among other things.