John Laurence Markle (December 25, 1941 — November 16, 1987) was an American murderer. Born to actress Mercedes McCambridge and novelist William Fifield, Markle took the surname of McCambridge's second husband, film and television director Fletcher Markle, who adopted the boy.

Markle and his wife had two daughters, and the family moved to Little Rock in 1979 after he went to work for Stephens, Inc., as essentially a one-man futures-trading department. Markle became a vice president after only eight months (faster than any previous associate), and the early performances of his accounts were exceptional. Friends called him a devoted family man, although they noted that, while his wife and daughters were involved in a range of community activities, the family was very private.

When questions had been raised about some of his accounts, Markle was placed on medical leave by Stephens in early October while the accounts were reviewed. That investigation, which led to the discovery of an extensive embezzlement scheme involving accounts belonging to his mother, resulted in Markle being fired on November 13, 1987.

Three days later, on November 16, Markle murdered his wife and two daughters before taking his own life.