But that's before tax.
Phelps, 31, could be forced to pay nearly 40 percent of that money, or up to $55,440, in a "victory tax" to the Internal Revenue Service, according to the Americans for Tax Reform.
The U.S. Olympic Committee awards its medalists $25,000 for a gold medal, $15,000 for silver, and $10,000 for bronze. The IRS treats those winnings as income, so winners must pay taxes on them.
While Phelps' finances aren't public, he has earned an estimated $94 million in endorsement deals over his career and has an estimated 2016 net worth of about $44.3 million, according to MoneyNation.com. Those endorsements put him in the top tax bracket.
The estimates are based on endorsement deals companies have struck with similar high-profile athletes and the exposure of the endorsements. A representative for Phelps did not respond to a request for comment.
Unlike professional baseball or football, swimming doesn't come with long-term, multimillion-dollar contracts.
Phelps' career medal winnings make up only an estimated 2 percent of his overall career income, said Tom Gerencer, MoneyNation's head writer and researcher.
Phelps will make an estimated $12 million in endorsements this year, according to Gerencer.
By contrast, swimmer Katie Ledecky, 19, who is attending Stanford University in the fall, cannot accept endorsement money due to NCAA regulations.
But that means Ledecky, of Bethesda, is also likely in a lower tax bracket and won't owe the IRS as much on her four gold medals and one silver in Rio.
"If she were paying the same amount, that would be a travesty, but she's not," Gerencer said. "She's not being taxed at that rate."
Depending on their annual earnings, some lesser-known U.S. Olympians could conceivably avoid having to pay any victory tax, he said.
"It's entirely possible that there are Olympians who are paying $0 in taxes on these medals because their income is much lower," Gerencer said.
Howe Burch, an executive vice president with TB&C Advertising in Baltimore and a former marketing executive with Reebok and Fila, said Phelps' victory tax is "probably rather insignificant for him."
"The guy just won another five or six medals and will have many opportunities and will appear in numerous marketing campaigns," Burch said. "I just don't think the tax obligation on his medals will be too much of a burden on him."
John Maroon, a Baltimore publicist who represents Cal Ripken Jr. and Under Armour founder Kevin Plank's Sagamore Ventures, called the Olympic victory tax "insulting and stupid."
He said the tax diminishes the U.S. Olympic Committee and shines a bad light on the country.
"I think it's absolutely ridiculous," he said. "I don't think they should be expected to pay taxes on the prizes they win."
Maroon doubted any U.S. Olympic medal-winner would complain about the tax. But he said the prize money should be tax-exempt as matter of national pride.
"Let them have their medal without paying for it," he said.
Congress is considering a bill to exempt Olympic winnings from federal taxes.
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