Ali Rıza Sergen Yalçın (born 5 November 1972, Istanbul) is a Turkish football manager, sports commentator and former international footballer. He currently serves as head coach of Süper Lig club Beşiktaş. One of only two players to have worn the jerseys of all four clubs known in Türkiye as the "Big Four" — Beşiktaş, Fenerbahçe, Galatasaray and Trabzonspor — he surpassed the 100-goal mark in the Süper Lig to join the "100 Goals Club". He is the only person to have won both the Süper Lig and the Türkiye Kupası as both a player and a manager for Beşiktaş.

Ali Rıza Sergen Yalçın was born on 5 November 1972 in Kilyos, a suburb of the Sarıyer district of Istanbul, as the first child of Günsel and Özer Yalçın. Inspired by his father, who was also a footballer, Yalçın joined Beşiktaş’s youth academy in 1982 at the age of ten. He trained under coach Serpil Hamdi Tüzün and was part of the team that won the Turkish Youth Championships in 1989.

Promoted to the first team in 1991 by then-head coach Gordon Milne, Yalçın made his official debut for Beşiktaş on 1 September 1991 against Gençlerbirliği and scored his first goal on 5 April 1992 during an away match against Konyaspor. During his first period at Beşiktaş (1991–1997), he became one of the club’s key players, winning two Süper Lig titles, one Türkiye Kupası, two Presidential Cups and one Prime Minister’s Cup. He left the club in 1997 at the end of his contract following financial disagreements with management.

^{Sergen Yalçın Siirt Jet-PA signing ceremony (AA)}

In June 1997, Yalçın transferred to İstanbulspor, then chaired by Cem Uzan. He made his first appearance for the club in the UEFA Intertoto Cup and contributed to their run to the semifinals. In late 1998, citing unpaid wages and disputes with management, he unilaterally terminated his contract. In January 1999, his registration rights were acquired by JetPA Holding, owned by Fadıl Akgündüz, and he signed a 3.5-year contract with Siirt Jet-PA Spor on paper.

^{Sergen Yalçın Fenerbahçe period (AA)}

Without ever playing for Siirt Jet-PA, Yalçın was loaned to Fenerbahçe in 1999. He made his debut for Fenerbahçe on 6 February 1999 against Gençlerbirliği. His loan agreement was terminated in December of the following season due to tactical disagreements and conflicts with head coach Zdeněk Zeman.

In accordance with Turkish Football Federation rules, which required a player to be registered with a third-party club to transfer between two Turkish clubs in the same season, Yalçın was officially registered as moving to Sloga Jugomagnat of North Macedonia and then loaned to Galatasaray at the start of 2000. During his half-season at Galatasaray, he won both the Süper Lig and the Türkiye Kupası. However, because he had played for Fenerbahçe in a European match earlier in the season, he was ineligible to feature in Galatasaray’s UEFA Cup-winning squad in 2000 under tournament regulations.

^{Sergen Yalçın Galatasaray period (AA)}

At the start of the 2000–2001 season, Yalçın moved on loan to Trabzonspor. With this transfer, he became the first player in Türkiye to have played for all four of the country’s major clubs. His time at Trabzonspor was marred by injuries and wage disputes with management, and he left the club at the end of the season. He was loaned back to Galatasaray for the 2001–2002 season and stood out with goals in the UEFA Champions League, but his campaign ended in February 2002 after tearing his cruciate ligaments.

^{Sergen Yalçın Trabzonspor period (AA)}

Before the 2002–2003 season, at the request of head coach Mircea Lucescu, his registration rights were acquired and he returned to Beşiktaş. In this season, marking Beşiktaş’s 100th anniversary, he became the club’s top scorer as they won the league title, scoring the historic goal that secured the championship in the match against Galatasaray. In the 2003–2004 season, he scored two goals in an away match against Chelsea in the UEFA Champions League, helping Beşiktaş win 2–0. On 6 August 2005, he netted his 100th goal in the Süper Lig against Kayseri Erciyesspor, entering the "100 Goals Club".

^{Sergen Yalçın second Beşiktaş period (AA)}

After winning the Türkiye Kupası in the 2005–2006 season, his contract with Beşiktaş was not renewed and he departed the club. In the 2006–2007 season, he transferred to Etimesgut Şekerspor, competing in the 2. Lig B Category. In 2007, he signed with Eskişehirspor. After one season with the club, he was released from the squad in 2008 and announced his retirement from professional football.

^{Sergen Yalçın National Team period (AA)}

Yalçın began his national team career in 1989 with the Turkey U-16 team. He was a key member of the U-21 national team that won the gold medal at the 1993 Mediterranean Games, scoring three goals in the tournament. He made his debut for the senior national team on 31 August 1994 against Macedonia. He was selected for Türkiye’s squads at UEFA Euro 1996 and UEFA Euro 2000 and played in both tournaments. Although he featured in the qualifiers for the 2002 FIFA World Cup, a pre-tournament injury prevented him from being included in the final World Cup squad. He earned 37 caps for the national team and scored five goals.

After retiring from active football, Yalçın began his managerial career in November 2008 as coach of Beşiktaş’s U-15 team. He managed Beşiktaş’s A2 team during the first half of the 2009–2010 season and in 2010 took on the role of sporting director at Sarıyer Spor Kulübü.

^{Sergen Yalçın Gaziantepspor managerial period (AA)}

Yalçın’s first Süper Lig managerial experience came in November 2013 at Gaziantepspor, where he remained until March 2014. In December 2014, he became head coach of Sivasspor, guiding the team to the semifinals of the Türkiye Kupası, but his contract was terminated in October 2015. He continued his managerial career with several Anatolian clubs: Gaziantepspor (2016), Kayserispor (2017), Eskişehirspor (2017), Konyaspor (2018), Alanyaspor (2018–2019) and Yeni Malatyaspor (2019–2020).

On 29 January 2020, Yalçın signed a 1.5-year official contract with Beşiktaş and assumed the head coaching position. In his first full season, 2020–2021, he led Beşiktaş to win both the Süper Lig title and the Türkiye Kupası. With this double trophy success, he became the first person in Beşiktaş history to win the Süper Lig title as both a player and a manager. Despite having his contract extended, he resigned from his position on 9 December 2021 following unsatisfactory results.

^{Sergen Yalçın Beşiktaş managerial period (AA)}

He returned to management on 2 January 2024 by signing with Antalyaspor, but left the club at the end of the 2023–2024 season. On 30 August 2025, he was appointed head coach of Beşiktaş for the second time and resumed leadership of the black-and-white team.

On 18 May 2026, following a meeting with club president Serdar Adalı, Yalçın announced his resignation. In his farewell statement, he said: "What did I do that these fans left me so alone? There is no point in continuing with every match overshadowed by protests. I do not seek compensation! I wish Beşiktaş all the success for the future."

After retiring from active football, Yalçın became heavily involved in sports media. He wrote columns for the newspapers Fanatik and Vatan and appeared as a football commentator on numerous media outlets including TRT 1, NTV, NTVSpor, Show TV, Kanaltürk, TRT Spor and Ekol TV.

He also gained recognition in television beyond football, serving as a judge on the talent show Yetenek Sizsiniz Türkiye, produced by Acun Ilıcalı. In 2014, he portrayed himself as a character named Sergen Yalçın in the TV series Sil Baştan. He has appeared in advertising campaigns for numerous brands.

In his private life, he is known for his interest in horse racing and owns several racehorses named "Sergen", "Kazım Baba" and "Blackberry". His brother, Gürsoy Yalçın, also came from the world of sports and passed away on 5 February 2025.