Sex segregation is the separation of people according to their sex.

The term gender apartheid (or sexual apartheid) also has been applied to segregation of people by gender, implying that it is sexual discrimination. In some circumstances, gender segregation is a controversial policy, with critics contending that in most or all circumstances it is a violation of human rights, and supporters arguing that it is necessary to maintain decency, sacredness, modesty, female safety, or the family unit.

In almost all parts of the world, places for activities which involve nudity – for example, showers, toilets, changing rooms – are usually segregated by sex.^{[citation needed]} There are exceptions to this: clothing-optional beaches and art classrooms for figure drawing are generally not segregated. Saunas and baths may or may not be, depending on the culture.

The degree of segregation can vary. In some places, separate changing rooms for men and women are the norm, while elsewhere, a single change room with cubicles is normal. With the widespread practice of groping women in crowded public places (e.g. street harassment or eve teasing), some countries have designated women-only passenger cars or compartments on trains.