Negative campaigning is the process of deliberately spreading negative information about someone or something to worsen the public image of the described. A colloquial, and somewhat more derogatory, term for the practice is mudslinging.

Deliberate spreading of such information can be motivated either by honest desire of the campaigner to warn others against real dangers or deficiencies of the described, or by the campaigner's dishonest ideas on methods of winning in political, business or other spheres of competition against an honest rival. However, if the mudslinging statements can be proved to be correct, mudslinging takes the moral dimension of an opponent's duty serving the greater good by exposing the weakness of the other candidate.

The public image of an entity can be defined as reputation, esteem, respect, acceptance of the entity's appearance, values and behaviour by the general public of a given territory and/or a social group, possibly within time limits. As target groups of public and their values differ, so negativity or positivity of a public image is relative; thus, to be successful, negative campaigning has to take into account current values of the group it addresses. The degree of strictness in practicing the group's values as opposed to its tolerance for violating the norms has also to be taken into consideration.