Sedition is overt conduct, such as speech and 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.

Because sedition is overt, it is typically not considered a subversive act, and the overt acts that may be prosecutable under sedition laws vary from one legal code to another.

Roman origin.

Seditio (lit. 'going apart') was the offense, in the later Roman Republic, of collective disobedience to a magistrate, including both military mutiny and civilian mob action. Leading or instigating seditio was punishable by death. Civil seditio became frequent during the political crisis of the first century BCE, as populist politicians sought to check the privileged classes by appealing to public assemblies. The Julio-Claudian emperors addressed this situation by abolishing elections and other duties of the assemblies. Under Tiberius the crime of seditio was subsumed in the law of majestas, which prohibited any utterance against the dignity of the emperor.

Seditio has often been proposed as the offense for which Jesus was crucified, as described in Luke 23:14: "inciting the people to rebellion" (Greek: ἀποστρέφοντα τὸν λαόν, "leading the people astray").

History in common law jurisdictions.

The term sedition in its modern meaning first appeared in the Elizabethan Era (1590) as the "notion of inciting by words or writings disaffection towards the state or constituted authority". The law developed in the Court of Star Chamber, relying on longstanding scandalum magnatum statutes and a broad repressive act of Mary the 1st against literature that contained "the encouraging, stirring or moving of any insurrection". That seditious statements were true was no defense, but rather an aggravating factor, since true statements were all the more potent. After the Star Chamber's dissolution, enforcement continued in the courts of assize and quarter sessions.

Three classes of seditious offense were commonly charged: "seditious words" manifested by speaking, "seditious libel" by writing or publishing, and "seditious conspiracy" by active plotting. Although England adopted the name of the offense from Roman-derived civil law, it did not rely on the jurisprudence.