Intrinsic motivation can be more influential for student's long-term learning because it can give students the internal drive to learn and complete a task without an outside influence. This study used a qualitative exploratory case study method and design. The problem addressed by this research study was that 9th and 10th grade social studies students lack motivation to learn. The purpose of this study was to explore the classroom instructional practices and strategies of 9th and 10th grade social studies teachers that played a role in their students' intrinsic motivation. The study used the self-determination theory framework to understand the intrinsic motivation strategies and practices teachers utilized to motivate students. The research questions addressed in this study were what classroom instructional practices and strategies high school teachers use to intrinsically motivate 9th and 10th grade students in social studies, what rationale do high school teachers provide for using the instructional practices and strategies, and what aspects of cognitive development of their 9th and 10th grade students in social studies do teachers consider when selecting instructional practices and strategies. The study used purposeful sampling to select nine high school teachers who teach 9th and 10th grade social studies. The data from this study was collected using semi-structured interviews. The responses were analyzed using the qualitative data analysis software NVivo. The data revealed three themes: the purpose of autonomy, the purpose of belonging, and the purpose of competence. In this study the evaluation and implications of the study findings resulted in identifying teacher strategies and practices that intrinsically motivated their students. The study results implied that teachers have a direct impact in determining effective practices and strategies to intrinsically motivate their students. A future research recommendation is to expand the research study to include student responses. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]