Martina Hingis celebrates her 39th birthday on September 30, 2019. “Forever Young” girl, Hingis bid adieu to tennis at the age of 37, thrice after calling it quits and making a return to the court she called her own since she was 14. Hingis initially retired after 2003 and then a second time in 2007. She said the final goodbye to the game in 2017. Hingis remains the Tennis world’s youngest Grand Slam champion in the Open era and second-youngest ever to lift a major title. Martina Hingis is also the youngest Tennis player to be World No 1.