Mob rule or ochlocracy (Greek: ὀχλοκρατία, romanized: okhlokratía; Latin: ochlocratia) is the rule of government by a mob or mass of people and the intimidation of legitimate authorities. Insofar as it represents a pejorative for majoritarianism, it is akin to the Latin phrase mobile vulgus, meaning "the fickle crowd" from which the English term "mob" originally was derived in 1680s, during the Glorious Revolution.

Ochlocracy is synonymous in meaning and usage to the modern informal term "mobocracy", which arose in the 18th century as a colloquial neologism. Likewise, the ruling mobs in ochlocracies may sometimes genuinely reflect the will of the majority in a manner approximating democracy, but ochlocracy is characterised by the absence or impairment of a procedurally civil and democratic process.

An "ochlocrat" is one who is an advocate or partisan of ochlocracy. It also may be used as an adjective ("ochlocratic" or "ochlocratical").