Portugal captain Ronaldo topped the influential business magazine’s list for the first time 12 months ago.
The Euro 2016 winner earned $93m (£72.05m) from salary, bonuses and endorsements last year.
The 32-year-old saw his earnings rise $5m (£3.87m) a year on.
The list of elite athletes consists of players from 11 different sports.
Basketball dominates with a record 32 NBA players among the top 100, up from 18 in 2016, followed by baseball with 22, American football with 15 and football with nine.
The top 100 athletes earned a total of $3.11bn (£2.4bn) over the last 12 months, a slight decrease from last year’s earnings of $3.15bn (£2.43bn).
List of top 10 highest-paid athletes in the world
- Cristiano Ronaldo – football ($93m/£72.05m)
- LeBron James – basketball ($86.2m/£66.79m)
- Lionel Messi – football ($80m/£61.98m)
- Roger Federer – tennis ($64m/£49.58m)
- Kevin Durant – basketball ($60.6m/£46.95m)
- Andrew Luck – American football ($50m/£38.74m)
- Rory McIlroy – golfer ($50m/£38.74m)
- Stephen Curry – basketball ($47.3m/£36.64m)
- James Harden – basketball ($46.6m/£36.10m)
- Lewis Hamilton – formula 1 ($46m/£35.64m)
Golfer Rory McIlroy is the highest-earning Briton on the list. His $50m (£38.74m) puts him in sixth place – of that, $34m (£26.34m) came from endorsements.
Wales international Gareth Bale, Ronaldo’s Real Madrid team-mate, remains the highest-earning British footballer, with his $34m (£26.34m) putting him 24th.
World number two tennis player Serena Williams is the only woman on the list, in 51st, with $27m (£20.92m) made last year.
Manchester United striker Zlatan Ibrahimovic in 30th with $32m (£24.79m), is the highest-placed Premier League footballer.