Sexology, a discipline that has evolved over the past 150 years, refers to the scientific study of sexuality. Academically, sexology spans the physical, biological, psychological/behavioral, and social sciences and typically includes the study of human sexual attitudes, interests, behaviors, development, problems, and aberrations. Today, sexology enjoys a position of respect in higher education in most nations – represented by academic departments, faculty appointments, majors and minors, undergraduate and graduate degrees, congresses, and a host of journals. In this entry, we present a brief history of sexology as well as select topics of interest, including psychosexual development, sexual and gender identity, sexual health, sexual response, and sexual problems as represented by the sexual dysfunctions and the paraphilias. For each topic, a brief description is provided, along with contemporary thought, developments, and issues surrounding the particular topic of study.