Self-made billionaire Denis O'Brien (60) initially made his fortune from Esat Telecom which he built up in the 1990s and sold to British Telecom Group in 2000 for €2.4bn.
He then went on to bring his telecoms expertise to the Caribbean with Digicel. It disrupted the market by bringing cheaper phones and plans to ordinary people. He owns 94pc of the mobile phone network provider which has now expanded into the Asia Pacific and Central America.
O'Brien also has investments in property, healthcare and hospitality, including the PGA Catalunya and Quinta do Lago resorts on the Iberian peninsula.
The richest individual born in Ireland, he was raised in Dublin. His father Denis O'Brien Snr, a successful businessman and an accomplished athlete, was a huge influence on him. Early in his career, O'Brien, who attended High School in Rathgar, Dublin and later UCD, worked for GPA boss and Ryanair co-founder, Tony Ryan.
One of O'Brien's early successes was winning a new radio licence for Dublin, 98FM, which he continues to own through Communicorp, also home to Today FM and Newstalk. O'Brien is also the largest shareholder in Independent News & Media, publisher of this newspaper and others. The media group is currently the subject of an investigation by the Office of the Director of Corporate Enforcement.
O'Brien's biggest asset is telecoms company Digicel which operates in 31 countries. For several years, the company was a massive cash cow for the entrepreneur, delivering O'Brien close to $1.5bn in dividends in the space of a decade.
Just before Christmas, Digicel closed a deal with its bondholders that will see $1.9bn of debt mature two years later than previously planned. The company had been in negotiations with bondholders for several months as it sought to restructure its $6.7bn debts.
In a tragic turn of events, group CEO Alex Matuschka von Greiffenclau died suddenly in December with O'Brien stepping in as interim CEO.
O'Brien owns the Beacon Hospital in Dublin. He is personally investing up to $450m (€395m) in a new venture, Deep Blue Cable, a network of undersea fibre optic cables linking dozens of countries in the Caribbean.
In 2015, he sold forecourt chain Topaz, receiving €258m in cash from a Canadian company, Couche Tard. He made an estimated €30m on the sale of the LXV building on the site of the former Canada House on Dublin's St Stephen's Green.
His Quinta do Lago resort in Portugal, which he bought for about €31m in 1998, is valued at over €220m. He owns Actavo, formerly known as Siteserv.
The businessman has significant philanthropic interests. Following the 2010 earthquake in Haiti - a key market for Digicel - he funded the restoration of Port-au-Prince's Iron Market and his Digicel Foundation built 150 schools.
O'Brien is a strong supporter of the Special Olympics and for a time paid the wages of the Republic of Ireland football team manager. He is also a major, but low-profile, supporter of Irish rugby.
Last May, he took delivery of a new $70m (€61m) corporate jet, less than three years after he last bought an identical one. The new Gulfstream G650 is among the world's most sought-after executive jets.
He owns a superyacht Nero and a luxury ski chalet in the French Alps called Chalet Chocolat Chaud (Chalet Hot Chocolate).