This timely volume examines the ways in which queer and trans theory are supported by recent findings from psychological science. In it, Ella Ben Hagai and Eileen Zurbriggen explore foundational ideas from queer thought and transgender theory including the instability of gender, variation in sexualities, intersectional theory, and trans writers’ rejection of the “born in the wrong body” narrative. These key ideas are juxtaposed with innovative empirical psychological research on the fluidity of gender, the proliferation of sexual identities, and transgender affirming medical and psychological care. This book explains the history and politics of key ideas shaping the study of the psychology of gender and sexuality today. It also describes the ways that the queer and trans* revolutions have changed how psychologists understand gender, sexuality, and transgender identities. It will be especially helpful for readers interested in interdisciplinary scholarship.