D enis O'Brien is Ireland's most famous and often controversial telecommunications tycoon. He made his first fortune by founding the mobile phone operator Esat Digifone, which won Ireland's second mobile license in a highly contentious bidding process. He sold the company to British Telecom in 2000 for a massive profit.

He then took his winnings and founded Digicel, a mobile phone network operator with a focus on emerging markets. He launched the company in Jamaica in 2001 and, through an aggressive expansion strategy, built it into the dominant mobile provider across the Caribbean, Central America, and the Pacific Islands. In addition to his telecom empire, he has significant interests in media, real estate, and other sectors. His career has been marked by both incredible business success and frequent controversy over his political connections and business dealings.