Gregory James McMackin (born April 24, 1945) is a retired American football coach and former player.
He served as the head football coach at Oregon Institute of Technology from 1986 to 1989 and at the University of Hawaii at Manoa from 2008 to 2011, compiling a career college football record of 53–39–1.
Before coming to Hawaii as defensive coordinator in 2007, he previously served in the same capacity for the Seattle Seahawks, the Miami Hurricanes, and the Texas Tech Red Raiders.