Euan Williams began training with Charlton at the age of seven before signing for the club's academy at U9 level.
In 2019, Williams joined fellow Addick Aaron Henry in the England U16 set-up, as the pair went on a training camp with the young Lions in Turkey.
The attacking midfielder penned his first professional contract with the club in February 2020.
Williams, who has also been capped by Northern Ireland at youth level, made his first-team debut for the Addicks in a Papa John's Trophy tie against MK Dons in January 2022.
In July 2022, he put pen-to-paper on a new two-year contract with the Addicks.