The Swiss tennis legend, a men's record 20-time Grand Slam singles champion, becomes the first player from his sport atop the annual list since its 1990 debut, rising from fifth in 2019.
Federer's haul over the past 12 months included $100 million from appearance fees and endorsement deals plus $6.3 million in prize money. His previous best showing was second in 2013.
"His brand is pristine, which is why those that can afford to align with him clamor to do so," University of Southern California sports business professor David Carter told the magazine.
The ongoing coronavirus pandemic that shut down sports worldwide caused the first decline since 2016 in the total income of the world's 100 top-paid athletes, a 9% dip from last year to $3.6 billion. Another plunge is expected next year from the shutdown.