Serena Williams finished as the WTA year-end singles No. 1 five times.
Her five year-end No. 1 seasons were 2002, 2009, 2013, 2014, and 2015. The first came after her breakthrough early-2000s period, when she won the French Open, Wimbledon, and US Open in 2002. She returned to the top at the end of 2009 after winning the Australian Open and Wimbledon and reaching the US Open final.
Williams then dominated the rankings in the middle of the 2010s. She ended 2013, 2014, and 2015 at No. 1, winning major titles in each of those seasons and producing especially strong results in 2015. Her total places her among the most frequent year-end leaders in WTA history.
A common mix-up is confusing year-end No. 1 finishes with total weeks ranked No. 1. Williams spent 319 weeks at the top, including a 186-week uninterrupted run from 2013 to 2016. She did not finish 2016 as No. 1; Angelique Kerber did.