Physics Education Research (PER) is a discipline-based education research field focused on understanding how people learn physics, how physics can be taught more effectively, and how to support individuals from all backgrounds to have meaningful learning experiences in physics. PER investigates the full continuum of participation in physics—from a person’s first encounter with science, whether inside or outside of school, through undergraduate and graduate studies, and into professional careers. Researchers in this field use both quantitative and qualitative methodologies to investigate how students think about physics, explore the social and cognitive processes involved in learning, and analyze the broader educational ecosystems that shape learners’ experiences. By drawing on theories from education, psychology, and learning sciences, PER researchers design and implement studies aimed at building evidence-based practices. The ultimate goal of PER is to foster deeper conceptual understanding of physics, improve learning outcomes, and enhance the overall experience of learning, teaching, and participating in physics.