The sex-positive movement is a social and philosophical movement that seeks to change cultural attitudes and norms around sexuality, promoting the recognition of sexuality (in the countless forms of expression) as a natural and healthy part of the human experience and emphasizing the importance of personal sovereignty, safer sex practices, and consensual sex (free from violence or coercion). It is based on the idea that "sexuality is an important part of the human experience and it deserves respect." Although the definition of the term greatly varies among those involved in the movement, its central notion is "openness to a variety of sexual orientations, interests (or lack thereof), identities and expressions." The sex-positive movement also advocates for comprehensive sex education and safe sex as part of its campaign. The movement generally makes no moral distinctions among types of sexual activities, regarding these choices as matters of personal preference.

The terms and concepts of sex-positive (German: sexuell positiv) (or, alternately sex-affirmative (sexuell bejahend)) and sex-negative (sexuell negativ) are generally attributed to Wilhelm Reich. His hypothesis was that some societies view the sexual expression as essentially good and healthy, while others have a generally negative view of sexuality and seek to repress and control libido. Other terms used to describe this concept include pro-sex or pro-sexuality.

The sex-positive movement does not, in general, make moral or ethical distinctions between heterosexual or homosexual sex, or masturbation, regarding these choices as matters of personal preference. Other sex-positive positions include acceptance of BDSM and polyamory as well as asexuality.

Some sex-positive theorists have analyzed sex-positivity in terms of the intersection of race/culture, gender, sexuality, class, nationality, and spirituality. Because of the vastness of the sex-positivity movement, it has been challenging for people to reach an agreed-upon definition of the term "sex-positivity". Several definitions of sex-positivity have been offered by sexologist Carol Queen:

Sex-positive, a term that's coming into cultural awareness, isn't a dippy love-child celebration of orgone – it's a simple yet radical affirmation that we each grow our own passions on a different medium, that instead of having two or three or even half a dozen sexual orientations, we should be thinking in terms of millions. "Sex-positive" respects each of our unique sexual profiles, even as we acknowledge that some of us have been damaged by a culture that tries to eradicate sexual differences and possibilities.

It's the cultural philosophy that understands sexuality as a potentially positive force in one's life, and it can, of course, be contrasted with sex-negativity, which sees sex as problematic, disruptive, and dangerous. Sex-positivity allows for and in fact celebrates sexual diversity, differing desires and relationships structures, and individual choices based on consent.

Calls for tolerance of sexual activity outside the established norms of the Western world have been present since antiquity. Commenting on the story of Pyramus and Thisbe, the humanist Giovanni Boccaccio wrote in the 14th century:

The passion of unbridled activity is the passion of desire, and is almost a plague and common crime among the young; in which - ah! - it must be tolerated with a patient mind, since it is so by the will of nature, that while we are able we voluntarily incline to procreation, lest the human race fall into defect if intercourse is postponed until old age.