Answer: Serena Williams
Notes: American tennis legend Serena Williams has announced that she will retire from professional tennis at the age of 40. Serena Williams won her first major title at the 1999 US Open, when she was 17. Since then, she won 23 Grand Slam singles titles, the most of any woman in the Open Era. She won her last Slam title at the 2017 Australian Open when she was eight weeks' pregnant. Serena has 73 WTA titles overall and 14 major doubles titles with sister Venus Williams.
