Billionaire investor George Soros had a lot to celebrate on Saturday evening: his 82nd birthday and the engagement to his much younger girlfriend Tamiko Bolton.

Soros and Bolton, who met in the spring of 2008, formally announced their engagement at a party at Soros' summer home in Southampton, New York attended by a small group of friends and relatives, according to a person familiar with the trader.

Soros proposed to Bolton, 40, a few weeks ago during a weekend visit to the Hamptons, a summer beachside colony on Long Island frequented by New York's wealthy.

For Soros, this will be his third marriage and the second for Bolton, who was married briefly in the 1990s. Soros has five children from his previous marriages.

Last year, Adriana Ferreyr ,a former girlfriend of Soros, filed a lawsuit in Manhattan state court, alleging he reneged on a promise to buy her an apartment. Soros has filed a pending motion to dismiss the lawsuit filed by the former Brazilian soap opera star.

Also in 2011, Soros, who is an active contributor to politically liberal causes and frequently speaks on world economic events, converted his hedge fund into a family office and stopped managing money for outside investors.

Soros rose to fame and fortune two decades ago on a now-historic trade, in which he took on the Bank of England and shrewdly wagered on a devaluation of the British pound.

Bolton, who once started an Internet-based dietary supplement business and is now running a web-based yoga education business, has a masters degree in business from the University of Miami.

The engagement ring Soros gave Bolton, according to a person close to the trader, is a Graff diamond in a platinum setting on a rose gold band.

Among the guests at the party at Soros' summer home were journalist Jane Bryant Quinn and Blackstone's Byron Wien.

Earlier this year, Reuters first reported that Soros' son Jonathan, who last September stepped down from day-to-day management of the affairs at Soros Fund Management, had decided to set-up his own family office. In moving to manage his own money, Soros' son also planned to take on key employee of Soros Fund Management, which last reported having about $25 billion in assets.