MOSCOW — Two decades ago, Dmitry E. Rybolovlev was a small-town hustler hoping to strike it rich amid the collapse of the Soviet Union. Today, he is one of the wealthiest men in the world, with a penthouse in Monaco, a yacht named “My Anna” worth more than $100 million, and two of the most expensive private residences in the United States.

Much of that money, it so happens, flowed through Cyprus.

His rapid rise was as typical for a Russian oligarch as is his deep dependence on Cyprus for offshore banking. Working in part through Cypriot trusts, Mr. Rybolovlev, a former doctor, sold his gigantic potash fertilizer mining conglomerate after a tumultuous and lucrative run as owner and spirited the money abroad. Then the good times rolled.

In 2008, Mr. Rybolovlev, now 46, bought a Florida mansion from Donald Trump for $95 million. At the time, this was the most ever paid for a private residence in the United States. Almost as an afterthought, he complained it was in such poor repair that it could not be inhabited.

A few years later, Mr. Rybolovlev bought the most expensive apartment ever sold in New York from the family of the former Citigroup chairman Sanford I. Weill, paying $88 million for the penthouse at 15 Central Park West.