Obscenity (in Latin obscenus, meaning "foul, repulsive, detestable"), is a term that is most often used in a legal context to describe expressions (words, images, actions) that offend the prevalent sexual morality of the time. It is often replaced by the word salaciousness.

Despite its long formal and informal use with a sexual connotation, the word still retains the meanings of "inspiring disgust" and even "inauspicious; ill-omened", as in such uses as "obscene profits", "the obscenity of war", etc. It can simply be used to mean profanity, or it can mean anything that is taboo, indecent, abhorrent, or disgusting.

The definition of obscenity differs from culture to culture, between communities within a single culture, and also between individuals within those communities. Many cultures have produced laws to define what is considered to be obscene, and censorship is often used to try to suppress or control materials that are obscene under these definitions: usually including, but not limited to, pornographic material. As such censorship restricts freedom of expression, crafting a legal definition of obscenity presents a civil liberties issue.

United States obscenity law

The United States has constitutional protection for freedom of speech, which is not interpreted to protect every utterance. The Supreme Court has found that, when used in the context of the First Amendment, the word "obscenity" is usually limited to content that directly refers to explicit sexual acts that are publicly accessible, though it has at times encompassed other subject matters, such as spoken and written language that can be publicly transmitted and received by the general public.

The legal term of obscenity is usually denoted to classify a distinction between socially permitted material and discussions that the public can access versus those that should be denied. There does exist a classification of those acceptable materials and discussions that the public should be allowed to engage in, and the access to that same permitted material—which in the areas of sexual materials ranges between the permitted areas of erotic art (which usually includes "classic nude forms" such as Michelangelo's David statue) and the generally less respected commercial pornography. The legal distinction between artistic nudity, and permitted commercial pornography (which includes sexual penetration) that are deemed as "protected forms of speech" versus "obscene acts", which are illegal acts and separate from those permitted areas, are usually separated by the predominant culture appreciation regarding such. The accepted areas are deemed to fit those sexual acts regarded as "normal", while the obscene areas are considered to be deviant or unworthy of public access. For example, in the United States currently, images of mere human nudity and single couple heterosexual vaginal-only penetration are listed as protected speech, while images showing anal and homosexual penetration are presently not.Fact: date=October 2007 However, no such specific objective distinction exists outside of legal decisions in federal court cases where a specific action is deemed to fit the classification of obscene and thus illegal. The difference between erotic art and (protected) commercial pornography, vs. that which is legally obscene (and thus not covered by 1st Amendment protection), appears to be subjective to the local federal districts inside the United States and the local moral standards at the time.