Emerging at Utrecht
Mertens first began to turn heads in his debut season at Utrecht in 2009/10. He scored seven goals in 39 appearances in all competitions and was runner-up to Ajax's Luis Suarez for the Dutch Footballer of the Year award.
Dutch dynamite at Eindhoven
Mertens signed for PSV Eindhoven in a dual transfer with Kevin Strootman, replacing the departing Balazs Dzsudzsak. The pair joined for a combined reported fee of €13million.
Mertens hit the ground running at his new club, scoring on his debut, though his sweet beginnings quickly turned sour as his side lost 3-1 to AZ Alkmaar.
On August 28, Mertens scored his first hat-trick for PSV in a 6-1 thrashing of Excelsior. Less than a month later, he scored four goals against Roda JC, cementing his status as one of the brightest prospects in the Eredivisie.
Mertens went on to score 21 goals in 33 appearances in his debut Eredivisie season - the fourth-highest goal tally in the league. In all competitions, Mertens scored 27 goals in 49 appearances in the 2011/12 season.
PSV won the 2011/12 KNVB Cup, beating Heracles Almelo in the final, and then beat Ajax 4-2 in the 2012 Johan Cruyff Shield.
Mertens scored 18 goals in 39 appearances across all competitions in his second season at PSV, his last with the club.
Moving to Naples
Mertens became Rafael Benitez's first signing as Napoli boss on June 16, 2013. The deal was reported to be worth €9.5million.
Mertens scored 13 goals in 47 appearances in all competitions in his first season at Napoli as the club won the 2013/14 Coppa Italia and 2014 Supercoppa Italiana.
Following the departure of Argentine striker Gonzalo Higuain to Italian rivals Juventus, Napoli boss Maurizio Sarri relied heavily upon Mertens for goals in the 2016/17 season. Mertens rose to the challenge, scoring 34 goals in 46 appearances in all competitions.
Mertens was prolific once again in 2017/18, scoring 22 goals in 49 appearances. Once again, however, Napoli were narrowly beaten to the Serie A title by Juventus. Sarri subsequently left to replace Antonio Conte as the head coach of Chelsea.
Meanwhile, Mertens remained at Napoli, scoring 19 goals in 47 appearances in all competitions during the 2018/19 season. That was followed by 16 goals in 42 appearances in 2019/20, complemented by another Coppa Italia.
In 2020/21, Mertens scored 10 goals in 38 appearances as Napoli finished fifth in Serie A, narrowly missing out on Champions League qualification.
Representing the Red Devils
Mertens played for Belgium at under-17 level and made his first senior appearance in 2011. He was part of the side at the 2014 World Cup in Brazil, then again at Euro 2016 in France and the 2018 FIFA World Cup in Russia.
In 2021, Mertens made Belgium's squad for the delayed Euro 2020 tournament, where his side were drawn against Denmark, Finland and Russia in the group stages.
Mertens gained negative publicity ahead of Euro 2012 after a push on England's Gary Cahill in a pre-tournament warm-up game resulted in the Chelsea defender being ruled out of the tournament.
"I think it was one of those things, a freak situation. I hit Joe (Hart), probably one of the worst people to hit in the whole team because his shoulders are massive. That was that. He didn't think, 'I'm going to push him and break his jaw.'
Personal life
Mertens was born in Belgium to soccer-loving parents, Marijke and Herman, who he notes as inspiration behind his career. Mertens is reportedly married to Kat Kerkhofs.
Net worth
Salary Sport reports that Mertens has earned a total of £33,592,000 over the course of his career, although his precise net worth is unknown.