Benoît Badiashile was born on 26 March 2001 in Limoges, France, and is of Congolese descent. He came through the academy system before joining AS Monaco, where he signed his first professional contract in February 2018. He made his senior debut for the club later that year, featuring in a Ligue 1 fixture against Paris Saint-Germain, and went on to establish himself as a reliable centre-back in the French top flight during his time at the Stade Louis II.
A composed, ball-playing centre-back, Badiashile reads the game well and is comfortable bringing the ball out from the back. His performances at Monaco attracted attention from across Europe, and in January 2023 he made the move to Premier League side Chelsea on a seven-and-a-half-year contract for a reported fee of £32.7 million. He marked his Chelsea debut with a clean sheet in a 1–0 win over Crystal Palace.
At Chelsea, Badiashile has gone on to add silverware to his record, winning the UEFA Conference League in 2024–25 and the FIFA Club World Cup in 2025. He was also named in the IFFHS Men's Youth World Team for 2021, recognition of his quality at the younger end of the senior game.
On the international stage, Badiashile represented France across age groups from under-16 onwards before earning his first senior call-up in September 2022 for UEFA Nations League matches against Austria and Denmark. He made his senior debut in the fixture against Austria that same month. He is also the younger brother of fellow professional footballer Loïc Badiashile.