In this chapter, we introduce energy justice, an emerging transdisciplinary concept capable of tackling complex energy problems. Energy justice is a term that has been used in practice (i.e. in non-academic work, such as in the commercial and public sectors) far longer than in academic research, albeit to a very limited degree. With the emergence of the energy justice concept, two approaches have come to dominate, one that considers energy systems using existing understandings of forms of justice, and one that deciphers its two main principles from the unique characteristics of energy as a good. To differentiate between these two approaches, we call them, respectively, the “system” and “foundational” approaches. The purpose of the chapter i...