Conor McGregor was born in Crumlin, a suburb of Dublin, Ireland.
McGregor moved with his family to Lucan, another Dublin suburb, when he was 12 years old. Shortly thereafter he took up a plumbing apprenticeship and began training in mixed martial arts.
He did not fight his first professional fight until he was 19.
McGregor will fight Floyd Mayweather, who is from Michigan, on Saturday in a much-hyped bout. The fight will take place at T-Mobile Arena in Las Vegas.
Mayweather is a heavy favorite to win. The fight is expected to start shortly after 11 p.m. ET.