The Spaniard won the French Open in 2016 before going on to lift the Venus Rosewater Dish on Wimbledon's Centre Court the following summer, but her career had looked to be in serious decline after not playing a competitive match since January 2023.
"If 25 years ago, when I started hitting my first tennis balls, someone had told me that I would become a professional tennis player, that I would fulfil my dream of winning Roland Garros and Wimbledon, that I would become No.1 in the world and win the WTA Finals, I would have thought this person was crazy," Muguruza told a news conference on Saturday.
"Tennis has given me a lot in this first part of my life. It has been a fantastic journey in which I have experienced unique situations. I have travelled all over the world and experienced many different cultures.
Spain's Muguruza also reached the Australian Open final in 2020. (Darren England/AAP PHOTOS)
"I am tremendously grateful to all the people who have helped and accompanied me throughout this chapter, because without them I would not have been able to get here.
"I have grown and matured in a very different way than what can be considered normal, and now I am ready to start a new chapter in my life, which will surely be linked in some way to tennis and sports."
Venezuelan-born Muguruza, who was announced as the newest Laureus Ambassador, turned professional in 2012 and reached her first grand slam final three years later at Wimbledon, where she was beaten by Serena Williams.
But the big-hitting Spaniard took revenge in 2016 when she stunned Williams in the final at Roland Garros, and, a year later, she beat Venus Williams to add the Wimbledon trophy to her collection.
She climbed to the top of the rankings in September 2017, where she stayed for four weeks, but consistency was not Muguruza's strong point and she slipped down the standings before a resurgence in 2020.
Muguruza reached her fourth grand slam final at the Australian Open, losing to American Sofia Kenin, and she returned to the world's top three at the end of 2021 after winning the WTA Finals for the first time.
But the next season saw her plummet back down the rankings and her retirement comes as no surprise given her long hiatus from the sport.
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