BackgroundEighty one percent of adolescents do not meet the recommended physical activity (PA) guidelines with levels of physical activity declining steadily with age and more pronounced in girls of low socioeconomic position (SEP). Furthermore, early adolescence is a time when the rate of decline in PA is most severe amongst girls, placing them at an increased likelihood of developing negative health outcomes associated with physical inactivity. In response, the aim of this study was to explore low-SEP pre-teen girls’ experiences of being physically active and to understand their perceptions of the individual, social and environmental factors that influence these experiences. MethodsFocus groups were conducted with 107 girls aged 10–12 years from four urban and three rural primary schools. Reflexive thematic analysis was used to analyse the data, with themes mapped to the relevant domains of the Theoretical Domains Framework (TDF). ResultsThemes highlighted how skills and confidence underpin girls’ self-identity for PA. Girls described how their social network (i.e., peers, family, coaches and teachers) shaped their experiences of being active. Girls recognised how being active was impacted by the challenges and opportunities in their local community (e.g., lack of facilities and anti-social behaviour). ConclusionThis study provides insight into low-SEP pre-teen girls’ experiences of being physically active in both rural and urban locations, while highlighting the complex interplay of individual, social and environmental factors. Additionally, the use of the TDF presents an in-depth behavioural diagnosis which can be used to inform future theory-based interventions to promote low-SEP pre-teen girls PA.