Maniac (from Greek μανιακός, maniakos) is a pejorative for an individual who experiences the mood known as mania. Also in common usage it is an insult for someone involved in reckless behavior.

The MANIAC (Mathematical Analyzer, Numerical Integrator, and Computer or Mathematical Analyzer, Numerator, Integrator, and Computer) was an early computer built under the direction of Nicholas Metropolis at the Los Alamos Scientific Laboratory. It was based on the von Neumann architecture of the IAS, developed by John von Neumann. As with all computers of its era, it was a one of a kind machine that could not exchange programs with other computers (even other IAS machines). Metropolis chose the name MANIAC in the hope of stopping the rash of silly acronyms for machine names, although von Neumann may have suggested the name to him.

Maniac is a 1980 American exploitation slasher horror film directed by William Lustig and written by Joe Spinell and C. A. Rosenberg. The plot focuses on a disturbed and traumatized serial killer who scalps his victims. Spinell also developed the story and stars as the lead character.