His death was announced by a spokeswoman for ReichmannHauer Capital Partners, an investment firm.
Mr. Reichmann and his brothers, Albert and Ralph, led Olympia & York, their family's real estate development firm, which counted among its greatest projects the World Financial Center in Lower Manhattan and Canary Wharf in London's East End. At their apex in 1990, the Reichmanns held about 8 percent of New York City's commercial office space, more than twice as much as their closest rival, the Rockefellers.
In all, Olympia & York owned 40 major office towers in a dozen cities on both sides of the Atlantic and controlled $20 billion in assets. The net personal worth of the Reichmanns reached $10 billion, making them at one point among the 10 wealthiest families in the world. But in 1992, they ran out of cash while building Canary Wharf, and their real estate business quickly collapsed.
Paul Reichmann, a tall, soft-spoken man who dressed in black suits, white shirts and dark ties, was clearly the family business strategist and chief decision-maker. He and his family were lavish contributors, mostly to Orthodox Jewish causes; they donated up to $50 million a year to yeshivas, synagogues and hospitals around the world.
Despite his austere demeanor, Mr. Reichmann took enormous business risks. He bet that each new development project could exceed the size of the previous one and still attract enough tenants to produce a windfall.
"For Paul, it is like being a gambler, like being a heroin addict he cannot stop," Andrew Sarlos, a prominent Toronto investment banker and Reichmann family friend, said in a 1988 article in Maclean's, the Canadian weekly.
Mr. Reichmann scoffed at that sort of criticism. "You don't get the returns if you don't take the risk," he said in an interview with Institutional Investor magazine in 2000.
For years, Mr. Reichmann's track record was so impressive that his creditors did not seem to mind his high-roller approach. His sense of timing in the notoriously cyclical real estate market seemed infallible, and he was viewed as a master negotiator with an uncanny understanding of financing techniques.
But the Reichmann empire crumbled in 1992. The immediate cause was the Canary Wharf project in London. With real estate prices plunging around the world, other major Reichmann properties were also in the red, and the family's stock market investments soured.
Crushed under debts of more than $20 billion, Olympia & York went bankrupt. The Reichmanns were left with a net worth of less than $100 million one of the most astonishing financial collapses in history.
Paul Reichmann blamed his own overconfidence. "The fact that I had never been wrong created character flaws that caused me to make mistakes," he said in 1997.
Mr. Reichmann and his family partly rebuilt their fortune. In a personal triumph, he recovered control of Canary Wharf in 1995, as a minority partner and chairman of an investment group that included George Soros and Laurence Tisch, and then pushed ahead with the completion of the project. He retired in 2005 after an alliance of developers led by Morgan Stanley acquired Canary Wharf.
The strains of commerce and religious orthodoxy were often inseparable in the family's ventures. For example, Olympia & York closed its construction sites on the Jewish Sabbath, paying overtime for Sunday labor, and during the Jewish religious holidays, as well as Christian ones.
At the height of his business career, Mr. Reichmann sometimes spoke wistfully of the Talmudic studies and religious school building projects he undertook as a young man.
"I think that what I did in those years was a greater achievement than what I've done since," he was quoted as saying in a 1996 biography of his family, "The Reichmanns," by Anthony Bianco. Paul Reichmann was born in Vienna on Sept. 27, 1930, the fifth of six siblings. His parents, Samuel and Rene, were Orthodox Jews who had moved from rural Hungary to Vienna, where they owned a prosperous egg export business. But Nazi Germany's annexation of Austria in 1938 forced the family to flee to Paris.
Two years later, when the Nazis overran France, the Reichmanns fled to Tangier, Morocco, where Samuel Reichmann became a successful currency trader.