Serena Williams is an American professional tennis player, widely considered one of the greatest tennis players in history. She has won 23 Grand Slam singles titles, the most in the Open Era, and has been ranked world No. 1 eight times. She also has a strong doubles record, including 14 Grand Slam titles in women's doubles and 2 in mixed doubles. Serena was born on September 26, 1981, in Saginaw, Michigan, and began playing tennis at the age of four, coached by her father, Richard Williams. She and her sister, Venus, were trained rigorously from a young age and turned professional in the mid-1990s. Serena holds the record for the most Grand Slam singles titles in the Open Era (23). She has won a total of four Olympic gold medals, including two in women's doubles and two in singles. She is the only professional tennis player to achieve a Career Golden Slam, both in singles and doubles. She completed a Career Grand Slam, winning all four Grand Slam singles titles.