We were at the same pool party, and his people came over to my table and said 'hey, Prince Harry wants to meet you,'" the swimmer said.
Lochte explained that the impromptu race was the royal's idea.
I just took off my shirt and we jumped in and we just started racing, he said.
Lochte says he's "kinda happy" the prince didn't invite him up for partying at a hotel suite. Photos leaked online show Harry naked and next to a woman during a game of strip billiards.
Lochte says he "didn't need that."
Las Vegas Sun columnist Robin Leach reports the prince stripped down to his jeans and gestured for others to clear the way for the contest at the XS nightclub pool at the Wynn resort.
As predicted, the 11-time Olympic medalist won.
After our race and everything we went our separate ways, Lochte said.
The race wasn't the prince's only paparazzi-worthy moment during a wild weekend partying in Las Vegas. Photos leaked online show the redhead naked and cozied up to an unidentified woman.
It's hardly the first time the prince -- who allegedly disrobed as part of a game of strip pool -- has been filmed in a compromising situation, The Associated Press reports.
The third-in-line to the throne was famously photographed wearing a Nazi uniform for a costume party, and in another photo gaffe he was seen cupping the breast of a female TV presenter.