Defamation (sometimes known as calumny, vilification, or traducement) is the oral or written communication of a false statement about another that unjustly harms their reputation, and usually constitutes a tort or a crime.^[1] In several countries, including South Korea^[2] and Sweden,^[3] communicating a true statement can also be considered defamation.

Under common law, to constitute defamation, a claim must generally be false and must have been made to someone other than the person defamed.^[4] Some common law jurisdictions also distinguish between spoken defamation, called slander, and defamation in other media such as printed words or images, called libel.^[5]

False light laws protect against statements which are not technically false, but which are misleading.^[6]

In some jurisdictions, defamation is treated as a crime rather than a civil wrong.^[7] The United Nations Human Rights Committee ruled in 2012 that the libel law of one country, the Philippines, was inconsistent with Article 19 of the International Covenant on Civil and Political Rights, as well as urging that “State parties [to the Covenant] should consider the decriminalization of libel”.^[8] In Saudi Arabia, defamation of the state, or a past or present ruler, is punishable under terrorismlegislation.^[9]

A person who defames another may be called a “defamer”, “libeler”, “slanderer”, or rarely a “famacide”.

The term libel is derived from the Latin libellus (literally “small book” or “booklet”).