Mamadou Sarr

Sarr began his football career at Étoile Sportive de Saint-Laurent-Blangy, before joining Lens, where his father plays. He then moved to Lyon in 2018. During the 2021–22 season, at only 16 years old, he established himself as a starter with Les Gones under-19 team. He thus played an important role in Lyon's triumph in the Coupe Gambardella alongside players like Hugo Vogel and Mohamed El Arouch. He scored in the quarter-final against Strasbourg, then in the semi-final against Troyes.

Lyon

On 27 May 2023, Sarr made his professional debut in Lyon's 3–0 Ligue 1 victory against Reims as a substitute, replacing Maxence Caqueret in the 83rd minute. On 18 January 2024, Sarr moved on loan to RWDM Brussels in Belgium until the end of the 2023–24 season, where he played 10 games, but could not prevent them from being relegated.

Strasbourg

On 22 August 2024, Sarr joined Ligue 1 fellow Strasbourg for a transfer fee of €10M and signed a five-year contract with the team.

Chelsea

On 9 June 2025, Sarr moved to Chelsea on an eight-year contract. On 25 June 2025, he made his Chelsea debut as a late substitute in the 3–0 group stage win over Espérance in the Club World Cup, a competition that Chelsea would go on to eventually win. However, on 1 August 2025, Chelsea announced that Sarr would be loaned out back to Strasbourg on a season-long loan. On 2 February 2026, Sarr was recalled by Chelsea. On 13 February 2026, he made his first ever start for Chelsea in the 4–0 away win against Hull City in the fourth round of the FA Cup. On 28 August 2026, Sarr moved to La Liga side Real Sociedad on a one-year loan deal.

Eligible to play with Senegal, Sarr chose France for his first selections for the youth team, even recovering the captain's armband on several occasions with the under-17s. In April 2022, he was selected with the France team for the 2022 UEFA European Under-17 Championship organised in Israel. He was a starter during the competition, where France was crowned as champions after defeating Netherlands 2–1 in the final thanks to Saël Kumbedi's brace. In November 2025, Sarr received his first call-up to the Senegal national team. On 19 December 2025, his request to switch international allegiance to Senegal was approved by FIFA. For the 2025 edition of the Africa Cup of Nations, Sarr was called up by Senegal as part of their 28 men squad. On 18 January 2026, he started and played the full 120 minutes of the final against Morocco as the replacement for the injured and suspended Kalidou Koulibaly as he helped Senegal to win their 2nd AFCON trophy in the country's history. Overall, Sarr played 3 times for the Senegal national team during this edition of the tournament. On May 21, 2026, Sarr was officially selected by Senegal's coach Pape Thiaw from his list of 28 players to participate in the 2026 FIFA World Cup.

Mamadou Sarr was born on 29 August 2005, and is the son of former Senegalese international Pape Sarr. Mamadou was born in Martigues, Bouches-du-Rhône, while his father was playing for Istres. Sarr spent most of his childhood living in Nord-Pas-de-Calais, following his father who spent a large part of his career at Lens.