The 2021 Primera B de Chile, also known as Campeonato Ascenso Betsson 2021 for sponsorship purposes, was the 67th season of the Primera B de Chile, Chile's second-tier football league. The season started on 3 April 2021. Coquimbo Unido were the champions, winning their fourth title in the competition as well as clinching promotion to Primera División with a 2–1 victory over Fernandez Vial on 13 November, the last matchday of the regular season.