The runaway leaders play against an inconsistent Nantes side knowing three points will give boss Thomas Tuchel his first title since joining the club at the start of the season.
PSG fluffed their lines for the first time on 7 April. A win at the Parc des Princes over Strasbourg would have furnished them with the title in a record 29 games. PSG drew 2-2.
On 14 April, a draw in Lille would have sufficed. PSG were walloped 5-1 - their heaviest league defeat for 10 years.
However, PSG are still 17 points clear of Lille and victory at Nantes will wrap up the race.
"We are going to be champions, but you have to lose in the right way," said Kylian Mbappe, who had two goals ruled out for offside.
"We can't lack personality like that, and concede three, four, five goals. Losing happens, but that is not normal."
Thomas Meunier put through his own net in the seventh minute to give the hosts the lead on Sunday night. But it was soon all square after Juan Bernat levelled.
But the defender went from saint to sinner. He was given a straight red card just before half-time for a foul on Nicolas Pepe.
After the pause the floodgates opened. Pepe, Jonathan Bemba, Gabriel Magalhaes and Jose Fonte were all on the scoresheet as PSG lost skipper Thiago Silva and Meunier to injuries.
"Putting five past PSG doesn't happen to everyone, even if they did only have 10 men," Pepe told Canal+ "But we played well. We've still got six matches left and we need to win at least three or four to be assured of the Champions League next season."