Javert (French pronunciation: [ʒavɛʁ]), no first name given in the source novel, is a fictional character and a main antagonist of Victor Hugo's 1862 novel Les Misérables. He was presumably born in 1780 and died on June 7, 1832. First a prison guard, and then a police inspector, his character is defined by his legalist tendencies, authoritarian worldview, and lack of empathy for criminals of all forms. In the novel, he persecutes the protagonist Jean Valjean after his violation of parole and theft from the child Petit Gervais.

Hugo writes that Javert is composed of two "simple" sentiments, which are "respect for authority" and "hatred of rebellion". In Javert's eyes, "murder, robbery, all crimes, are only forms of rebellion". He also "(envelops) in a blind and profound faith everyone who had a function in the state, from the prime minister to the rural policeman". Reflective thought is "an uncommon thing for him, and singularly painful" because thought inevitably contains "a certain amount of internal rebellion".

He is without vices, but upon occasion will take a pinch of snuff. His life is one "of privations, isolation, self-denial, and chastity—never any amusement".

Javert has been described as a legalist: His "moral foundation... is built strictly on legalism"; he is "one of the most tragic legalists in Western literature" and "the consummate legalist".

Born in a prison (his mother, a fortune-teller, and his father serving in the prison galleys), Javert sees himself as excluded from a society that "irrevocably closes its doors on two classes of men, those who attack it and those who guard it". He becomes a law officer on the basis of "an irrepressible hatred for that bohemian race to which he belong[s]" and a personal foundation of "rectitude, order, and honesty". So devoted is he to this choice that, Hugo writes, "[h]e would have arrested his own father if he escaped from prison and turned in his own mother for breaking parole. And he would have done it with that sort of interior satisfaction that springs from virtue."

Following his encounters with Jean Valjean during the June Rebellion, in which he is first spared by Valjean and, later, spares him arrest, Javert experiences a deep torment caused by the compromise of his previous worldview. Where previously he has "never in his life known anything but one straight line", Jean Valjean's behavior compels him to see two lines, "both equally straight" and "contradictory". The profound confusion caused by the realizations that the law is not infallible, that he himself is not irreproachable, and that there exists a superior force (identified by Hugo with God) to what he has known, plunges him into such a despair that he commits suicide.

The character of Javert is loosely based on Eugène François Vidocq, a criminal and adventurer who became a police official (though Vidocq wrote that he never arrested anyone who stole out of need). Hugo also drew on Vidocq's life for the character of Valjean. In the novel, Hugo describes Javert as "a marble informer, Brutus in Vidocq".

Javert first becomes familiar with the convict Jean Valjean as an assistant guard in the Bagne of Toulon. Years later, in 1823, the fugitive Valjean is living under the name Monsieur Madeleine and serving as the mayor of a small town identified as Montreuil-sur-Mer, where he is a successful manufacturer. Javert arrives in 1820 to serve as an inspector with the local police. Javert suspects Madeleine's true identity and becomes convinced of it when he watches Madeleine demonstrate extraordinary strength by lifting a loaded cart off of a man trapped beneath it. Madeleine also antagonizes Javert by dismissing his attempt to arrest Fantine, a prostitute detained for having a violent row with a street idler. Javert decides to denounce Valjean as an ex-convict, but learns from Parisian authorities that they have already arrested someone who calls himself Champmathieu; the authorities believed Champmathieu is really Valjean.