ISTANBUL — Serena Williams ended her best season in style, rallying past Li Na 2-6, 6-3, 6-0 on Sunday for her second straight WTA Championship and 11th title of the year.

She became the first player to successfully defend the WTA title since Justine Henin in 2007.

This was Williams’ fourth WTA Championship. She also won the elite tournament of the eight top-ranked players in 2001, 2009 and 2012.

Williams has won 78 of 82 matches this year. She will finish the year as the top-ranked player for the third time, the others in 2002 and 2009.

Li was in her first WTA Championship final and will finish the year at a career-high No. 3.