Maximus (also known as Maximus the Mad) is a supervillain appearing in American comic books published by Marvel Comics. The character has been depicted both as a member of and antagonist to the Inhumans. Created by writer Stan Lee and artist Jack Kirby, he first appeared in Fantastic Four #47 (February 1966).

Iwan Rheon portrayed Maximus in the Marvel Cinematic Universe miniseries Inhumans. Additionally, Mark Hamill, Nolan North, and Diedrich Bader have voiced the character in animation.

Maximus first appeared in Fantastic Four #47 (February 1966), and was created by Stan Lee and Jack Kirby.

Maximus, an Inhuman, was the second son of two of Attilan's top geneticists, Agon, the head of the ruling Council of Geneticists, and Rynda, director of the Prenatal Care Center. Subjected to the DNA-altering Terrigen Mist when he was an infant, Maximus peculiarly showed no outward sign of any mutagenic change. As he matured, he hid his developing psionic powers from the community, but was less successful at disguising his antisocial tendencies.

When he was about sixteen, his elder brother Black Bolt was released from the protective chamber in which he had been confined since birth due to the destructive nature of his powers. One of Maximus's first responses to his brother's freedom was an unsuccessful attempt to make him release his power and prove Black Bolt could not control his sonic powers, and thus lose his freedom. A month later, Black Bolt witnesses Maximus making a treacherous pact with an emissary of the Kree, the alien race responsible for genetically accelerating the Inhumans eons before. In an attempt to stop the fleeing emissary so that he could be questioned by the ruling council, Black Bolt uses his forbidden power of the quasi-sonic scream and blasts the alien ship out of the sky. When the ship crashes to Earth, it landed on the parliament building, killing several key members of the Genetics Council, including the boys' parents. The reverberations of Black Bolt's voice also affects Maximus, addling his sanity and suppressing his nascent mental powers. When Black Bolt assumes the throne shortly thereafter, Maximus vows to oppose his brother and eventually usurp his rule.

Maximus stages his first successful coup a few years later. By performing an illegal experiment on the Alpha Primitives, the subhuman worker clones that once served the Inhumans, Maximus creates the Trikon, three bodiless energy beings of great destructive power. While the Trikon wreaks havoc in Attilan, Maximus successfully drives the Royal Family of Inhumans out of the city. Maximus later sends Gorgon in search of the amnesiac Medusa. In the several-year interval before Black Bolt and his cousins locate her in America, Maximus rules Attilan in Black Bolt's stead. Secure in his position, Maximus has his servant, the Seeker, locate the Royal Family and bring them back to Attilan. Upon doing so, Black Bolt seizes the crown back, to Maximus' dismay. Maximus also encounters the Fantastic Four for the first time. Maximus, hoping to win back the public's affection, activates the Atmo-Gun device he has been working on, a machine he believes will kill the human race and leave all other living beings intact. Maximus miscalculates, however, and the device has no effect. Out of spite, Maximus uses the device to erect a barrier around Attilan, imprisoning the entire race inside. Black Bolt liberates his people by using his quasi-sonic voice to destroy the barrier, at the price of devastating Attilan's ancient architecture.

Maximus then allies himself with six Inhuman criminals, sentenced for their treachery and subversive acts by Black Bolt with his verdict being interpreted by Oracle. Freeing Falcona, Aireo, Stallior, Nebulo, Leonus, and Timberius from their place of imprisonment with the Hulk's aid, Maximus then tricks the Hulk into breaching the protective barrier guarding a forbidden chemical substance created by the Inhuman scientist Romnar centuries ago. This substance had certain highly unstable energy absorbing capacities and Maximus intends to use it to usurp the throne again, but Black Bolt overpowers him before he can do so.

Maximus succeeds in bringing about his second coup some months later. Drugging the Royal Family with will-deadening "hypno-potions", Maximus takes the crown from Black Bolt and has the Royal Family imprisoned. Before he can activate his Hypno-Gun, which he believes will make all mankind surrender to his will, the Royal Family escapes and subdues him. Escaping Attilan with his band of renegades in a rocket, Maximus lands in the South American country of Costa Salvador, and attempts to build a will-deadening device similar to his Hypno-Gun. His plans are opposed by the Hulk and the United States Army, however, and he and his allies are forced to flee again.^{[volume & issue needed]}