Manchester United and Leeds United are two of the English Premier League’s most popular and historically successful clubs, and together constitute one of English football’s most interesting and inexplicable rivalries. English popular opinion claims that this rivalry is based on the Wars of the Roses and the royal houses of Lancaster and York, so this thesis engages with this idea and analyzes the rivalry's connections to this medieval historical event. Furthermore, the top flight English football league's evolution into the English Premier League brought social and economic changes to the sport, both at a broad and ground level, and this thesis finds out how much these changes affected this rivalry. All in all, this thesis analyzes medieval, social, cultural, and economic historical connections to one of English football's most unique club rivalries.