The list is dominated by athletes from America's NFL, NBA and Major League Baseball competitions, although the top five athletes - Mayweather, Messi, Cristiano Ronaldo, Conor McGregor and Neymar - are from either football or combat sports.
Note: Forbes' earnings include prize money, salaries and bonuses earned between 1 June 2017 and 1 June 2018. Footballer Lionel Messi took second place with earnings of $111 million (£82.7m) while Cristiano Ronaldo dropped from first place to third, with earnings of $108 million (£80.4 million).
Mayweather only boxed professionally once in 2017, defeating UFC star Conor McGregor via a 10 round technical knockout in an August clash.
Mayweather now has been the highest-paid athlete four times in the last seven years.
Mayweather overtook soccer star Cristiano Ronaldo, who held the money crown the previous two years.
Forbes said tennis' female sportspersons Li Na, Maria Sharapova and Serena Williams were list regulars but Li retired in 2014 and Sharapova is still dealing with the aftermath of a 15-month suspension for using a banned substance.
Swiss ace Federer remains the most attractive athlete for sponsors, with endorsement deals accounting for $65 million of his earnings.
The top 100 has an global flavour with athletes from 22 countries, but Americans dominate the action with 66 making the cut thanks to sky-high salaries in baseball, basketball and football.
LeBron James (basketball), Roger Federer (tennis), Stephen Curry (basketball), Matt Ryan (American football) and Matthew Stafford (American football) concluded the top 10. The 100 top-paid athletes - coming from 23 different countries with an average age of 31 - earned a collective $3.8 billion over the past year, with 65 of those athletes hailing from the United States.
Lewis Hamilton came in at number 12 with earnings of US$51m, making him the highest ranking racing driver on the list.
NBA stars lead with a record-topping 40 basketball players among the top 100.
Forbes said it was harder than ever to qualify for the 100 highest-paid athletes, with the cutoff up $1.5 million to $22.9 million.