TMZ Sports has learned the "Golden Eight" collection, created by renowned artist Brian Fox -- known for his ability to capture celebs and athletes -- is being shopped for $2 MILLION!!!

Each of the eight exquisite pieces, commissioned by owner Todd Patkin in '08, was inspired by a moment from the Games ... and all have been signed by Phelps.

“This collection was one of the most complex works of art I’ve ever had to capture on the canvas,” the acclaimed artist said.

“With every stroke, my goal was to not only portray the energy and power of Phelps while he was swimming, but also shine his individual personality through his famed swimming expressions.”

Fox has painted some of the most iconic stars, including Jackie Robinson and Muhammad Ali. He's also the artist behind the  "Miracle on Ice" painting depicting the American hockey team that defeated the mighty Soviets in 1980.

Of course, Phelps had the greatest Olympic Games in the history of the global competition. Michael entered 8 events, and won gold in every single won. Eight for eight:

100-meter butterfly
200-meter butterfly
200-meter freestyle
200-meter individual medley
400-meter individual medley
4x100 meter freestyle relay
4x200 meter freestyle relay
4x100 meter medley relay

Phelps retired with 23 gold medals, and 28 in total ... cementing himself as arguably the greatest Olympian ever.

U.S. Olympic Hall of Famer and 3x Olympic gold medalist Rowdy Gaines, now the voice of swimming in America, talked about the importance of the works of art.

"Brian Fox is the G.O.A.T. of sports artists. His 8 paintings of Michael representing his perfect 8 for 8 at the Beijing Olympics are the most beautiful pieces of sports art I have ever seen."

Gaines continued ... "They represent every detail of Michael's historic swims and I was so honored to get to know Brian and witness these amazing paintings up close and personal. These will be priceless one day and Brian will continue to show his brilliance for years to come."