Michael Phelps Lists Arizona Home For $4.1 Million

Michael Phelps is about to strike gold again ... this time on his Arizona home, which he's hoping to sell for $1.6 million more than he paid for it.

Phelps bought the house in Scottsdale a couple years back for $2.5 million. The 5-bedroom, 7-bath spread was brand spanking new at the time. It's now listed for $4.125 million.

The former Olympian and his wife, Nicole, welcomed baby no. 2 in February, so it's possible they're looking to expand ... although this pad ain't exactly small at 6k square feet. There are also 4 fireplaces and a 350-bottle wine storage.