This study is motivated by the demand for the transformation of basic education in response to the challenges of the 21st century, particularly in developing elementary school students’ critical reasoning through the implementation of the Merdeka Curriculum. This curriculum emphasizes student-centered learning and is grounded in an epistemological framework that views knowledge as the result of learners’ active construction. The study aims to analyze the epistemological foundations of the Merdeka Curriculum at the elementary school level, its implementation in the learning process, and its role in fostering students’ critical reasoning. The research employs a library research method with a descriptive qualitative approach. Data sources consist of official Merdeka Curriculum documents, as well as relevant national and international books and journal articles on educational epistemology and the development of critical reasoning. Data analysis was conducted using interpretative and critical content analysis techniques. The findings indicate that the Merdeka Curriculum is grounded in a constructivist epistemology, enriched by pragmatic and empirical approaches, thereby supporting contextual, project-based learning oriented toward students’ learning experiences. The curriculum plays a positive role in cultivating students’ critical reasoning; however, its implementation still faces challenges related to teachers’ readiness, school culture, and students’ adaptation. It can be concluded that strengthening teachers’ epistemological understanding and providing support from the educational ecosystem are key factors in the successful implementation of the Merdeka Curriculum in developing elementary school students’ critical reasoning.