Serena Williams a professional tennis player. She has won 23 Grand Slam singles titles, the most by any player in the Open Era, and the second-most of all time behind Margaret Court (24). The Women's Tennis Association (WTA) ranked her singles world No. 1 on eight separate occasions between 2002 and 2017. On her sixth occasion, she held the ranking for 186 consecutive weeks, tying the record set by Steffi Graf. In total, she has been WTA No. 1 for 319 weeks, which ranks third in the Open Era behind Graf and Martina Navratilova.

Williams is widely regarded to be one of the greatest female tennis players of all time. She holds the most Grand Slam titles in singles, doubles, and mixed doubles combined among active players. Her 39 Grand Slam titles put her joint-third on the all-time list and second in the Open Era: 23 in singles, 14 in women's doubles, and two in mixed doubles. She is the most recent female player to have held all four Grand Slam singles titles simultaneously (2002–03 and 2014–15) and the third player to achieve this twice, after Rod Laver and Graf. She is also the most recent player to have won a Grand Slam title on each surface (hard, clay and grass) in one calendar year (2015). She is also, together with her older sister Venus, the most recent player to have held all four Grand Slam women's doubles titles simultaneously (2009–10). Williams has won a record of 13 Grand Slam singles titles on hard court. Serena Williams is the name people think of when they think of tennis.