Michael Phelps didn't just take a beating in the 200m butterfly recently ... he also got his ASS kicked by the real estate market -- letting go of his swank Baltimore condo for $400,000 less than what he bought it for.
Phelps purchased the 4,080 sq. ft. home in Fells Point back in 2007 for $1.69 million -- but then the housing market crashed ... and so did the value of his home.
The 19-medal-winning swimmer listed the 3-bedroom pad earlier this year for $1.42 million -- but even that was asking too much ... because when he finally sold the place last week ... he could only get $1.25 mill.
For the mathematically challenged, that's a loss in value of $440,000 -- but it's just a drop in the bucket ... the guy's agent once predicted Phelps would earn roughly $100 million during his lifetime from endorsements.
Oh yeah, He's also THE GREATEST OLYMPIAN OF ALL TIME!