Lisp Machine Lisp is a dialect of the Lisp programming language, a direct descendant of Maclisp, and was initially developed in the mid to late 1970s as the systems programming language for the MIT Lisp machines.

Lisp Machine Lisp itself branched into 3 dialects. Symbolics named their variant ZetaLisp. Lisp Machines, Inc. and later Texas Instruments would share a common code base, but their dialect of Lisp Machine Lisp would differ from the version maintained at the MIT AI Lab by Richard Stallman and others.