Communications entrepreneur Denis O'Brien (59) first made his fortune by building up telecoms firm Esat in the late 1990s before selling it to BT, netting about €317m in cash.
Now the richest individual born in Ireland, his biggest asset is telecoms company Digicel which found success by bringing low-price mobile phone services to the emerging markets. It operates in 31 countries in the Caribbean and Asia Pacific.
In 2017, the company announced a restructuring plan to ready it for a shift towards data services, and, last summer, bonds in the company surged on renewed earnings growth, a signal that the plan will bear fruit.
The company, which pulled plans to float in 2015, has been a massive cash cow for the entrepreneur, delivering O'Brien close to $1.5bn in dividends in the last decade.
He has other interests in media, hospitality and services. He is personally investing up to $450m into a new venture Deep Blue Cable, a network of undersea fibre optic cables linking dozens of countries in the Caribbean.
O'Brien, who was born in Cork and raised in Dublin, has sold some assets in recent years, making impressive returns.
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 St Stephen's Green.
Last year, he sold a site in Dublin's Donnybrook that has been earmarked for a €60m-plus development of 90 luxury apartments to Cairn Homes.
His Quinta do Lago resort in Portugal, which he bought for about €31m in 1998, is valued at over €220m and is being upgraded and expanded. He owns Actavo, formerly known as Siteserv.
O'Brien, who attended UCD, is a keen sportsman and he has paid the wages of the Republic of Ireland football team manager and is also a major, but low profile, supporter of Irish rugby. He has always been a strong supporter of the Special Olympics.
The businessman has significant philanthropic interests, and, last November, Forbes wrote about his humanitarian efforts in the Caribbean following the devastation caused by hurricanes Irma and Maria.
In terms of media assets, he owns Communicorp, which includes 98FM, Today FM and Newstalk, and is a shareholder in Independent News & Media, publisher of this newspaper and others. He owns the Beacon Hospital.
He owns a €65m Gulfstream G650ER, a superyacht Nero and a luxury ski chalet in the French Alps called Chalet Chocolat Chaud (Chalet Hot Chocolate).
The billionaire always has an eye for what's the next big thing. The purchase of the Beacon being an example, as an aging population increases the demand for quality healthcare providers.