| Number of studies (k): 125 | Effect size: Standardized Mean Differences | ABSTRACT: Academic motivation is an essential predictor of school success in K-12 education. Accordingly, many meta-analyses have examined variables associated with academic motivation. However, a central question remains unanswered: What is the relative strength of the relations of both student variables (achievement, socioemotional variables, and background variables) and instructional variables (teacher variables, interventions, and technology) to academic motivation? To address this question, we conducted a systematic review of meta-analyses of constructs that focus on the question “Do I want to do this activity and why?” We included 125 first-order meta-analyses published before January 2021, with 487 first-order effect sizes, that investigated variables associated with academic motivation in K-12 education and were based on more than 8,839 primary studies and comprised almost 25 million students. We computed second-order standardized mean differences (SMD) using a two-level meta-analysis with robust variance estimation, considering moderators and including the methodological qualities and publication status of the meta-analyses. Our results showed that student variables (SMD = 0.39) and instructional variables (SMD = 0.43) had medium and similar second-order effect sizes. Of the student variables, socioemotional variables (SMD = 0.52) and achievement (SMD = 0.46) were more important than background variables (SMD = 0.19). Of the instructional variables, teacher variables (SMD = 0.61) were more important than interventions (SMD = 0.36) and technology (SMD = 0.35). Overall, the results provide the field with a clearer depiction of which student and instructional variables relate most closely to students’ academic motivation and thus have implications for the design of future interventions to foster students’ academic motivation in school.