Trying to become the first women's tennis player to win all four Grand Slams in one calendar year since Steffi Graf did it in 1988, Williams won the Australian Open, French Open, and Wimbledon before falling in the semifinals of the U.S. Open to Flavia Pennetta.
Winning three of the four Grand Slams brought Williams to 21 career Grand Slams, just one shy of Graff's 22.
Here she is on the cover:
Sports Illustrated
Williams becomes the first tennis player since Chris Evert in 1976 to win SI's Sportsperson honor during their playing career:
Billie Jean King also won the award in 1972. Arthur Ashe won the award in 1992, after he retired.
In the cover story for magazine, S.L. Price perfectly summed up Williams' dominance in 2015:
Williams, 34, won three major titles, went 53-3 and provided at least one new measure of her tyrannical three-year reign at No. 1. For six weeks this summer-and for the first time in the 40-year history of the WTA rankings-Williams amassed twice as many ranking points as the world No. 2; at one point that gap grew larger than the one between No. 2 and No. 1,000. Williams's 21 career Grand Slam singles titles are just one short of Steffi Graf's Open-era record. Such numbers are reason enough for Sports Illustrated to name Serena Williams its 2015 Sportsperson of the Year.
Is there reason to think she won't do it again in 2016?