Finals Day started with the doubles final, where Hsieh Su-Wei and Peng Shuai finished up on top.
Hsieh and Peng defeated Sara Errani and Roberta Vinci for their fifth WTA doubles title together.
The singles final followed, with Serena Williams' win streak on the line against Victoria Azarenka.
Azarenka had beaten Williams in their last meeting, but before that one had lost nine straight.
Though many of the games were close, Williams won almost all the big points to build a 61 42 lead.
The World No.1 was lethal from all sides during the match - serves, groundstrokes, net, speed...
Azarenka found momentum late in the match, breaking back for 61 43 and leading 40-15 on her serve.
The Williams camp - including sister Venus and mother Oracene - watched Serena in her element.
With one last backhand winner - her 41st winner of the match - Williams sealed a 61 63 victory.
Williams extended her winning streak to 24 matches, the longest winning streak of her career.
Williams also improved to 12-2 against Azarenka and an amazing 58-15 lifetime against Top 3 players.
Williams is 16-0 on clay in 2013 and 33-1 on clay since the start of 2012's clay court season.
Williams now has five WTA titles this year and 51 in her career - including eight clay court titles.
Only Anabel Medina Garrigues and Venus Williams have more clay court titles than her with 10 and 9.
Williams will hang onto No.1 through Roland Garros and will go into the grass court swing at No.1.