The legendary American swimmer, who has captured a record 28 Olympic medals, retired after the 2016 Rio Games.
Now he has set his sights on success as a businessman, hoping to see the stars of the 2020 Olympics and beyond opt for his swimwear in what is a cut-throat commercial environment.
"I am finished (as a competitor)," 31-year-old Phelps said on Thursday in Paris where he was launching his designs.
In a partnership with US manufacturer Aqua Sphere, which started in 2014, Phelps said he felt reinvigorated by his new career.
"It has become a passion in which I invest a lot of time and energy. I enjoy being around sports and swimming. It will be like this for the rest of my life and I love that."
In Rio, Phelps swam in his own self-designed gear as he won five more golds and a silver medal to confirm his status as a legend of the Olympics.
"I was more confident in my swimming by wearing my own gear," he explained having originally retired from competitive swimming after the 2012 London Olympics.
His 20 years' experience of the sport will be key to business success, he added.
"I sit around a table and have meetings with designers and engineers - it's a crazy experience.
"I didn't have this possibility before of someone listening to what I have to say about a product."
Phelps claims that some of Australia's highly-rated swimmers were interested in his designs last year but were unable to use them so as to avoid a conflict of interest with an existing sponsor.
"Technology and sport will continue to grow," added the American. "For me the dream will become the reality by having some of the best swimmers in the world wearing our suits."
Meanwhile, Phelps said that Paris hosting the 2024 Olympics "would be very special" but admitted that his heart naturally was with the Los Angeles bid.
The two cities as well as Budapest are vying to host the Games in seven years' time with a decision to be made by the International Olympic Committee in September.
"Having the Games in Paris would be very special, but I cannot lie. I am a little biased.
"The US is my country so I support Los Angeles for 2024."