An increasing number of individuals openly identify as non-binary (i.e., not exclusively female or male). Accordingly, psychological research on non-binary identities has expanded rapidly. We review key insights from this growing literature, first examining work that has demonstrated links between beliefs about the true nature of gender and/or sex (gender/sex) and feelings toward non-binary people. We also review research on non-binary people's self-concepts, which has shown the inadequacy of binary-focused gender/sex measurement practices for effectively studying non-binary people's lives and has suggested treating gender/sex as multidimensional. Then, we consider scholarship on non-binary people's wellbeing, including work exploring sources of joy and pleasure in non-binary people's lives (e.g., gender euphoria). Finally, we discuss recent advances in gender-inclusive theories and methods.