John Mark Karr (born December 11, 1964 in Conyers, Georgia) is a pedophile who made a false confession regarding the unsolved murder of six-year-old JonBenét Ramsey. Authorities were made aware of Karr via e-mails he exchanged over the course of four years with Michael Tracey, a journalism professor at the University of Colorado. They eventually located and identified Karr through telephone calls he was lured into making to Tracey.

Karr was arrested in Bangkok, Thailand, on August 16, 2006, by Thai authorities, then released to U.S. agents and flown first to Los Angeles, California, then to Boulder for further investigation. On August 28, prosecutors announced they had decided not to pursue charges in connection with the murder after DNA tests failed to place Karr at the scene, although serious doubts had been expressed about the veracity of his admission even before the tests were conducted. Karr was held in Boulder until September 12, 2006, when he was transported to Sonoma County, California to face unrelated misdemeanor child pornography charges. The charges were dismissed by a California judge on October 5, 2006, and Karr was immediately released.

Karr was born in Conyers, Georgia and spent his early childhood in Atlanta. His father, Wexford Karr, married Patricia Elaine Adcock on August 21, 1958, when he was 37 and she was 18. Wexford filed for divorce in 1973, eleven years into marriage, saying the marriage was "irretrievably broken," and that the boys were in his custody. Soon after, Wexford Karr, then 52 years old, married 29-year-old Susan Simpson, his neighbor in the same apartment complex. His marriage with Simpson ended in divorce six months later.