A leucotome or McKenzie Leucotome is a surgical instrument used for performing leucotomies, prefrontal lobotomies and other forms of psychosurgery.

Invented by Canadian neurosurgeon Dr. Kenneth G. McKenzie in the 1940s, the leucotome has a narrow shaft which is inserted into the brain through a hole in the skull, and then a plunger on the back of the leucotome is depressed to extend a wire loop or metal strip into the brain. The leucotome is then rotated, cutting a core of brain tissue. This type was used by the Nobel prize-winning Portuguese neurologist Egas Moniz.