This study aims to develop Augmented Reality (AR)-based flashcard learning media for renewable energy material for junior high school students and to evaluate its validity and initial practicality. The research employed the Rowntree development model, consisting of planning, development, and evaluation stages. Needs analysis conducted at SMP Negeri 1 Indralaya showed that 64% of students experienced difficulties in understanding renewable energy concepts, while 88% expected more innovative learning media such as AR-based flashcards. The prototype was evaluated through expert validation, one-to-one evaluation, and small group evaluation. Expert validation results indicated that the media met the feasibility criteria, with scores of 80% for design (valid), 92.31% for media (highly valid), and 100% for material (valid). The practicality evaluation showed excellent results, with the one-to-one evaluation obtaining an average score of 97.47% and the small group evaluation achieving 96.89%, both categorized as very practical. Students also responded positively to the ease of use, visual presentation, material comprehension, and perceived support for critical thinking. However, these student responses represent perceptions of the media and do not constitute direct evidence of students' critical thinking performance. Therefore, the findings support the validity and initial practicality of the developed AR-based flashcards, while further studies involving objective measures of critical thinking, such as pretest-posttest assessments and appropriate comparison designs, are needed to determine their effectiveness in improving students' critical thinking skills.