Conor McGregor is one of the most bankable stars in UFC - his rags to riches story has inspired millions around the world, but his loud mouth and quick temper has a habit of landing him in hot water.
Born in Crumlin in Dublin in 1988, McGregor took up boxing at the age of 12 but was unemployed and surviving on benefits by the time he began training in mixed martial arts (MMA) in 2006.
He signed a contract with UFC in 2013, and as well as his success in the ring - which earned him the nickname "The Notorious" - he draws big crowds for trash-talking his opponents.
In 2016, he became the first UFC fighter to hold two belts after taking the lightweight title while he was still reigning featherweight champion.
Last summer he made history and dominated headlines for months after tempting US boxer Floyd Mayweather out of retirement for a crossover fight in Las Vegas which netted him a reported $100m (€81m).
Although the fight was stopped in round 10 and Mayweather declared the victor, some of the biggest names in boxing praised his attempt, with Lennox Lewis saying he had "nothing to be ashamed of".
He sparked anger on the promotional tour when he told the Afro-American boxer "Dance for me, boy" - a phrase that has racial overtones
Mayweather later accused him of racism, saying: "He totally disrespected black women. He called black people monkeys."
McGregor responded by claiming:"(Mayweather) is trying to sway people in his favour and it's a cheap move."
After the defeat, McGregor did not stay out of trouble for long. In November he started an altercation with a referee at the Bellator MMA 187 event in Dublin when he leapt into the cage to celebrate his friend Charlie Ward's apparent victory.
Referee Mark Goddard took exception to McGregor's actions, ordering him out of the octagon and sparking a melee by pushing him away.
McGregor retaliated by running after Goddard and shouting and pointing at him before he was escorted out.
Having earned his cash, McGregor has never been ashamed of splashing it and frequently posts Instagram pictures of himself and his family on private jets, yachts and exclusive resorts and his fleet of luxury cars - including his Rolls Royce Ghost sprayed with the word Notorious.
He was threatened with legal action by a Solihull businessman behind a luxury car rental firm who claimed the fighter had damaged a Rolls Royce Wraith by posing standing on the bonnet.
Cars seem to be McGregor's weakness - last autumn he was fined €400 for being clocked driving at 158kph (98mph) on a road near Dublin on March 31.
He was eventually ordered to attend Blanchardstown District Court after he tried sending business associates in his place on two previous occasions.
McGregor has been with his partner Dee Devlin since 2008 and the couple have an 11-month-old son, Conor McGregor Jr, who frequently stars alongside his father in his social media posts.