The 6 highest-paid fighters in 2019

Even at 40 years old, Manny Pacquiao remains competitive at the elite level in world boxing.

He stopped Lucas Matthysse in July, last year, romped to a big win over Adrien Broner in January, and now takes on the undefeated Keit Thurman this summer.

Read more: Manny Pacquiao's next opponent Keith Thurman has pushed back against Deontay Wilder's controversial comments, saying boxing is 'not about killing people'

Pacquiao has fought 70 times as a pro fighter, appearing on pay-per-view an extraordinary 24 times. This has generated 20 million sales, or $1.25 billion, Forbes reports.

Deontay Wilder is one of the key reasons heavyweight boxing is experiencing a renaissance in the American market.

He has poor technique, but his power is so extraordinary it seems no man can escape a mid-fight clobbering at some point.

Wilder fought the unbeaten British fighter Tyson Fury in December, last year, and earned more than $10 million.

Read more: Watch Deontay Wilder knock out Dominic Breazeale in round 1 and send a violent message to Anthony Joshua

He recently vanquished Dominic Breazeale after attracting criticism for his controversial kill comments, and has rematches lined up against Luis Ortiz and Fury.

Conor McGregor is known around the world as a mixed martial artist, but Forbes says he is making an increasing amount of cash from his sponsorship deals and his whiskey business.

The Irishman is one of the fight game's most captivating characters because of his merciless trash talk, his showboating in the cage, and his concussive punching.

Last October, he returned to the Octagon for the first time in almost two years but was convincingly beaten by lightweight rival Khabib Nurmagomedov. He reportedly earned a guaranteed $3 million, according to Forbes, with an extra $30 million generated because of the event's popularity at the box office.

Read more: What whiskey 'unicorn' Conor McGregor is actually like, according to his Proper No. Twelve business partner

McGregor's whiskey brand, Proper no. Twelve, is proving a hit with consumers. His business partner Ken Austin told Business Insider that the company had sold around 200,000 cases. There are even plans to create more expressions as it looks to rival Jameson's as the most popular Irish whiskey on the market.

With his hulking physique, chiselled abdominals, and million dollar smile, Anthony Joshua is a blue-chip sponsor's dream.

He has deals with many big-name companies including Under Armour, Jaguar LandRover, and Beats by Dre.

Joshua was a silver medalist at the World Amateur Championships in 2011, a gold medal winner at the 2012 Olympic Games, and the unified heavyweight boxing champion until earlier this month when he was upset in the seventh round of an up-and-down barnburner with Andy Ruiz Jr.

Read more: Anthony Joshua's humiliating setback proves he should have listened to Floyd Mayweather 2 years ago

Joshua and Ruiz Jr. are expected to fight again later this year.

Saul "Canelo" Alvarez, a technically-gifted Mexican boxer, has regularly featured in the best-selling pay-per-view fights of all time.

His popularity is what convinced the market-disrupting streaming service DAZN to pay $365 million for 11 of Alvarez's bouts, the first of which was an easy knockout win over Rocky Fielding, before a decision victory over Daniel Jacobs, last month.

Read more: Sharpened defence, impressive punch resistance, and elite counter attacks: This is how Canelo Alvarez romped to a huge win over Daniel Jacobs to unify three boxing titles

Alvarez has a two-fight rivalry with hard-hitting middleweight Gennady Golovkin, with one win and one draw over the Kazakh puncher. It is likely a third fight will be booked soon.