A description of the meaning and terminology as well as population estimates of nonbinary gender identities is given. Respectful use of language, names and pronouns of people who identify as nonbinary is discussed. The chapter further includes the need for access to gender-affirming care and barriers to care; gender-affirming medical treatment interventions, including hormone treatment, speech and language therapy, hair removal and surgeries for bodies assigned female at birth (AFAB) and for bodies assigned male at birth (AMAB); and the importance of fertility preservation for this specific patient population.