Dries "Ciro"[4][5] Mertens (Dutch pronunciation: [dris ˈmɛrtəns]; born 6 May 1987) is a Belgian professional footballer who plays as a forward or winger for Süper Lig club Galatasaray.

As a youth, Mertens played for Stade Leuven, Anderlecht and Gent, and made his debut on loan to Eendracht Aalst in the Belgian Third Division.

Two years later, Mertens and teammate Kevin Strootman were transferred to PSV Eindhoven for a combined fee of €13 million, and won the KNVB Cup and Johan Cruyff Shield in 2012.

He spent five years in the youth setup at Anderlecht before being released in 2003, with coaches finding him to be too short and physically incapable of competing at a professional level.

[8] The coaching staff at Gent, much like those at Anderlecht before, remained unconvinced of Mertens given his slight frame, however, and loaned him out again the following season, this time to AGOVV Apeldoorn in the Netherlands.

Mertens' form prompted AGOVV, led by new manager John van den Brom, to exercise the option to sign the Belgian permanently the following season.

[12] In his debut season with the club, Mertens netted six league goals en route to being named runner-up to Ajax's Luis Suárez for the Dutch Footballer of the Year award.

In June 2011, it was announced that Mertens had signed for fellow Eredivisie club PSV Eindhoven as a replacement for the departing Balázs Dzsudzsák in a dual transfer with Utrecht teammate Kevin Strootman for a combined fee of €13 million.

[18] Towards the back end of the campaign, Mertens lost a number of teeth during a collision with Heracles goalkeeper Remko Pasveer, although he managed to score during the incident.

It was revealed on social media platform Twitter that Pasveer had found one of Mertens' teeth lodged in his head three weeks after the players had collided.

He also scored three goals in four KNVB Cup matches, including a header in the final at De Kuip, Rotterdam, leading PSV to a 3–0 win over Heracles.

[28] In the final of the Coppa Italia on 3 May 2014, Mertens replaced Marek Hamšík in the 64th minute and went on to score in stoppage time, securing a 3–1 win over Fiorentina.

[38][32] His form for club and country was rewarded when, on 30 December, he was named Belgian Footballer of the Year for 2016, beating Chelsea's Eden Hazard and Radja Nainggolan of Roma to the award.

[44] He then made his 200th Serie A appearance for the club on 14 April 2019 in a 3–1 win over Chievo, marking the occasion with an assist for Kalidou Koulibaly's opening goal.

Later that day, he started in the Coppa Italia final against Juventus, and was later substituted for Milik in the second half; Napoli won 4–2 on penalties following a 0–0 draw after regulation time.

[63] He made his first appearance in Belgium's opening match of the World Cup, replacing Chadli at half time and scoring a late winner in a 2–1 victory over Algeria in Belo Horizonte.

[69][70] Under new manager Roberto Martínez, Mertens scored five goals in Belgium's qualification for the 2018 FIFA World Cup, including two in an 8–1 home win over Estonia on 13 November 2016.

[75] Mertens was part of the Belgian squad for the 2022 World Cup in Qatar, where the team performed badly, failing to make it out of the group stages.

On 17 March 2023 new Belgian coach Domenico Tedesco dropped Mertens from the squad for European Championship qualifying games, citing the player's lack of match fitness.

[77][81] His favoured role is as a winger on the left flank, a position which allows him to cut into the centre and strike on goal from outside the area with his stronger right foot,[77][82] although he is also capable of playing on the right, and has even been used as an attacking midfielder by manager Dick Advocaat.

[77] During the 2016–17 season, following the departure of Gonzalo Higuaín to rivals Juventus and an injury to the club's main striker Arkadiusz Milik, Napoli coach Maurizio Sarri frequently deployed Dries Mertens either as a main striker, or in a false nine role, seemingly positioned as a lone centre-forward, rather than as a left winger, where he had previously faced competition from Lorenzo Insigne for a starting position; Sarri's tactical change was met with great results, and Mertens's goalscoring output increased dramatically as a result of this switch.