This chapter focuses on three different categories of mental disorders related to sexuality and gender: sexual dysfunctions, gender dysphoria, and paraphilic disorders. In general, sexual dysfunctions affect one’s ability to function sexually or to experience sexual pleasure; gender dysphoria describes distress experienced due to incongruency between one’s experienced gender (i.e., the internal, psychological experience of one’s gender) and one’s assigned gender (i.e., how one’s gender is perceived by others based on outward appearance); and paraphilic disorders are characterized by atypical, intense, and persistent sexual interests that cause distress or harm (or risk of harm). Typically, clinicians working in the area of sex therapy or sexual medicine will see clients with sexual dysfunctions and/or gender dysphoria, whereas clinicians who specialize in forensic psychology will see clients with paraphilic disorders given that these disorders often entail legal consequences.