Human sexual development begins prenatally and spans the entire lifetime. From fetal hormones that influence expressed sex to nascent sexual discovery in toddlers, to dramatic physical changes during puberty and sexual intimacy in adulthood, sexuality undergoes change throughout every major stage in life. In fact, some developmental stages are partly defined by sexual changes, for example, menarche, spermarche, menopause, and andropause. With sexual formation and identity being such integral parts of the human experience, it is no surprise that prominent thinkers have reflected upon the process of sexual development. The earliest, and among the most influential, was Sigmund Freud who iterated five stages of psychosexual development. To better appreciate Freud’s thinking, an understanding of his social context and theoretical perspective is helpful. This entry describes ...