HARLIE is the abbreviation for the fictional Human Analog Replication, Lethetic Intelligence Engine (originally Human Analog Robot Life Input Equivalents), an Artificial Intelligence which appears in the David Gerrold science fiction novel When H.A.R.L.I.E. Was One (1972; a significantly revised edition subtitled Release 2.0 (and changing the meaning of the acronym) appeared in 1988). Only time will tell whether a "Release 3.0" will follow, as "2.0" is as dated now (more dated, in some ways) as the original was in 1988.

Other differences between the original novel and the revision involve changing attitudes about sex and recreational drugs. (In the original, marijuana is available commercially, with common brand names including "Highmaster.")

HARLIE is one of the most realistic visions of advanced Artificial Intelligence encountered in the arts, on a par with HAL 9000. However, HARLIE is a more endearing version of HAL; while seemingly more humane than HAL in his actions and responses, he definitely has a different, often even inhumane way of approaching problems, and has an agenda of his own to follow. HARLIE's story revolves around his relationship with David Auberson, the psychologist who is responsible for guiding HARLIE from childhood into adulthood. It is also the story of HARLIE's fight against being turned off, and the philosophical question whether or not HARLIE is human.