This introduction proposes opacity as a generative and necessary frame for contemporary feminist and queer politics. Theorized by the Martinican philosopher and poet Édouard Glissant, opacity can be understood as an incalculable alterity that is at once the relational ontology of the world, an ethical demand, a form of political legitimation, and a poetics. In this “In Practice” collection, opacity is offered as an alternative to the familiar terrain of identity, visibility, and representation in feminist and queer politics and writing. Contributors utilize opacity as both a tactic and a material condition to address issues of surveillance, the nonhuman, and contemporary art. Jennifer Rhee considers clothing that evades drone detection, while Zach Blas and Jacob Gaboury discuss biometric facial recognition and masked protest. Jasmina Tumbas and Jemima Wyman claim camouflage as a refusal of the female body's objectification and also a catalyst for collectivization. Heather Davis argues that plastic is an opaque queerness, and Nathan Lee writes on the condition of being HIV undetectable as an optimistic imperceptible relationship to one's body. Across these texts, opacity operates as an expansive theory, politics, and aesthetics that works against the totalizing gaze of global surveillance and also demands a place for the nonhuman in feminist and queer thought.