Mert Müldür

Müldür is right-footed and began playing for Rapid Wien II as a right-back, although he is also known to play in the left-back position and as an attacker. Müldür is known for his sliding tackles, speed, stamina and aerial abilities which can make him play in a centre-back position. Through utilization of both feet, he can also successfully distribute passes from the back, which is considered an important feature of the new generation of defenders.

Born in Austria to Turkish parents, Müldür is a youth international for Turkey. He made his debut for the senior Turkish national team on 11 October 2018 in a 0–0 friendly draw against Bosnia and Herzegovina. At UEFA Euro 2024, Turkey's first and last goals were ignominiously credited to Müldür: he began his country's goal tally with a volley against Georgia in the group stage opener and scored the decisive own goal against the Netherlands in the quarter-finals. On 2 June 2026, Müldür was selected in the 26-man squad for the 2026 FIFA World Cup.

Rapid Wien

Müldür joined the SK Rapid Wien youth academy at the age of six in 2006, and worked his way up into the professional team. He made his professional debut for SK Rapid in a 4–1 Austrian Football Bundesliga loss to FC Red Bull Salzburg on 13 May 2018. On 29 May 2018, Müldür signed his first professional contract for three years with Rapid Wien.

Sassuolo

On 20 August 2019, Müldür signed for Italian club Sassuolo. He made his debut five days later, coming on as a substitute in a 2–1 away loss against Torino. On 15 August 2022, he suffered an ankle fracture injury against Juventus and missed 16 matches.

Fenerbahçe

On 2 August 2023, Müldür signed a four-year contract with Fenerbahçe until 2027. He made his debut with the team in a 3–0 UEFA Europa Conference League win over NK Maribor on 17 August 2023. On 21 August 2023, he made his Süper Lig debut with the team against Samsunspor in an away game, Fenerbahçe won 2–0. On 2 February 2026, he made his 100th appearances in all competitions for Fenerbahçe against FCSB in 1–1 UEFA Europa League away draw.

Müldür is a longtime fan of Fenerbahçe since his childhood. Müldür is multilingual, speaking five languages fluently: Turkish and German as main languages, English in education, also Bosnian and Serbian fluently because of his Serbian girlfriend, whom he has been with for many years.