Olympique Marseille were the biggest team in France in the 1980s and early 1990s. They won four French league titles back to back between 1989 and 1992. They also won the 1993 league season, but were stripped of the title due to bribery allegations.
PSG was formed in 1970 and they reached a TV deal in 1991 that gave them enough money to challenge Marseilles. Le Classique was born.
The rivalry between Marseille and PSG is fierce and has often led to violence. Marseille are the only French team to win the Champions League (they won it in 1993) and their fans were worried that their rivals, PSG, would equal that feat this year.