A by-election was held in the UK parliamentary constituency of Batley and Spen on 1 July 2021, following the resignation of the previous Member of Parliament (MP) Tracy Brabin, who was elected Mayor of West Yorkshire on 10 May. Under the devolution agreement, the position holds the powers and responsibilities of a police and crime commissioner, meaning the occupant of the office cannot simultaneously sit as an MP. The by-election was the fourth of the 58th Parliament, elected in 2019.

Tracy Lynn Brabin is a British politician who has served as the Mayor of West Yorkshire since the office was established on 10 May 2021. She previously was the Member of Parliament (MP) for Batley and Spen from 2016 to 2021 under the Labour and Co-operative banner.