For the purpose of this chapter, it is important that we first review what is understood by the term ‘men’. Historically and conventionally, the terms ‘man’ and ‘male’ have referred to sex but this has often been conflated with gender, resulting in ‘sex’ and ‘gender’ being used interchangeably. In recent times, our understanding of the differences between sex and gender has evolved. Sex refers to the biological characteristics (chromosomes, genitalia, hormones) that categorize people into male or female. Gender, however, is understood as a social construct that reflects a range of feelings, beliefs, and behaviours that a person may experience and exhibit, along a male–female spectrum. Other chapters in this book focus solely on the mental health of individuals whose sex was assigned male at birth (usually due to the appearance of their external genitalia) and who identify with the male gender. Some individuals, however, do not identify with the sex that was assigned to them at birth. In discussing gender dysphoria in men, this chapter, therefore, departs from the conventional definition of men to also include individuals who were not assigned male at birth but do identify as male. There is increasing awareness of the importance of inclusivity (Kaplan et al., 2018), and that a discussion about the mental health care needs of men must also include the needs of men who were not assigned male at birth.