M. Roy "Slab"[1] Jackson (February 12, 1876 – January 22, 1944) was an early professional football player who played for the Duquesne Country and Athletic Club.

Prior to his professional career, Jackson played college football at the University of Pennsylvania.

Roy, an avid foxhunter, also kept pleasure horses and was responsible for bringing the Penn--Marydel foxhound, to America.

Jackson's son, also named Roy, would go on to own the famous race horse, Barbaro.

He died on January 22, 1944, and was interred at West Laurel Hill Cemetery in Bala Cynwyd, Pennsylvania.