What three time defending female champion has ranked number one in Women's Singles tennis?
2015 US Open – Women's Singles Serena Williams was the three-time defending champion, but she lost in the semifinals to unseeded Roberta Vinci. In doing so, Williams missed the opportunity to become only the fourth woman (after Maureen Connolly, Margaret Court and Steffi Graf) to complete a calendar year Grand Slam by winning the tournament. She was also trying to set a new Open Era record by winning her seventh US Open singles title.
2006 Australian Open – Women's Singles Serena Williams was the defending champion, but she lost in the third round to Daniela Hantuchová.