Jackson DeForest Kelley ( January 20 , 1920 â `` June 11 , 1999 ) was an American actor famous for his role as Dr. Leonard McCoy of the USS Enterprise in the television series Star Trek and six movies that followed , as well as an older Admiral Dr. Leonard McCoy , Star Fleet Surgeon General Emeritus , in the Star Trek : The Next Generation television pilot , Encounter at Farpoint . Jackson DeForest Kelley ( January 20 , 1920 â `` June 11 , 1999 ) was an American actor known for his iconic roles in Westerns and as Dr. Leonard `` Bones '' McCoy of the USS Enterprise in the television and film series Star Trek .