The Okinawan-born 31-year-old, a nine-time winner on the U.S. LPGA Tour, told a Tokyo news conference she had made the decision last summer that this season would be her last.
"I actually began feeling this four to five years ago, and at that point I basically had to keep going while groping for some way to deal with it," she said.
Her coach told her that many players came to a point in the careers when they lose some motivation for the game and asked her to try to find a way through it.
"So I fought on for four years, but I couldn't really admit to myself that the motivation wasn't coming back, and I wasn't able to practice enough or throw myself into training ... The ideal I wanted just wasn't there anymore," she added.
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Miyazato won five titles in her rookie season on the domestic Japanese tour in 2004 before joining the elite U.S. LPGA circuit on a full-time basis two years later.
She won her first LPGA title at the 2009 Evian Masters in France, a victory she said remains one of her favourite memories, and rose to number one in the world rankings the following year.
With a slow, simple swing that made her one of the cleanest ball-strikers in women's golf, Miyazato finished her career without winning a major, the closest she came tied for third at the Women's PGA Championship (2006, 2010) and Women's British Open (2009).
She claimed the last of her 25 professional victories at the NW Arkansas Championship in 2012.
"To have the best results takes a lot of energy, and I know that well," she said. "I made this decision based on feeling that I'd reached my limits."
Miyazato smiled for most of the news conference, but her voice broke and her eyes grew shiny as she described the widespread support she'd received during her 15 years as a pro.
"I was very happy as a player," she added.
Miyazato gave no hint of her future plans, saying that she had the rest of the season left to play and that deciding to call it quits has actually given her more motivation.
"Now it would be nice if I can return the support I've been given in a new way," she added.
(Editing by Peter Rutherford)
