Seditious conspiracy is a crime in various jurisdictions of conspiring against the authority or legitimacy of the state. As a form of sedition, it has been described as a serious but lesser counterpart to treason, targeting activities that undermine the state without directly attacking it.

Sedition is overt conduct, such as speech or organization, that tends toward rebellion against the established order. Sedition often includes subversion of a constitution and incitement of discontent toward, or insurrection against, established authority. Sedition may include any commotion, though not aimed at direct and open violence against the laws. Seditious words in writing are seditious libel. A seditionist is one who engages in or promotes the interest of sedition.