Reading motivation has been defined consistently as a multidimensional construct. However, there is some disagreement regarding the number and nature of the dimensions of reading motivation. In particular, there is a lack of studies investigating the dimensional structure and measurement invariance (e.g., across gender) of reading motivation questionnaires. Based on earlier instruments, qualitative findings referring to students' reasons for reading, and theoretical considerations, we developed the Reading Motivation Questionnaire (RMQ). A sample of 883 sixth-grade students was presented with 34 reading motivation items pertaining to seven dimensions. Five of these dimensions (i.e., curiosity, involvement, grades, competition, social recognition) referred to Wigfield and Guthrie's Motivations for Reading Questionnaire, whereas two dimensions (i.e., emotional regulation, relief from boredom) were based on recent qualitative findings. The results from confirmatory factor analyses supported the hypothesized factor structure. In addition, three higher order factors were identified: intrinsic, extrinsic, and regulatory reading motivation. Moreover, strict measurement invariance across female and male students and across groups with low versus high reading competence was established. Construct validity of the RMQ was supported by the contributions of the RMQ factors to reading amount, fluency, and comprehension and by the predicted gender differences in the dimensions of reading motivation.