Mauricio Pochettino's men were given the opportunity to go top after pacesetters Lille were held to a goalless draw at fourth-placed Monaco. But they were undone in 10 second half minutes by Randal Kolo Muani.
The champions unsurprisingly were quickly onto the front foot at the Parc des Princes against a side floundering in the drop zone.
Angel Di Maria brought a fine save from Nantes goalkeeper Alban Lafont in the 14th minute and from the resulting corner Marquinhos should have done better with a free header.
⏱️ 14'
— Paris Saint-Germain (@PSG_inside) March 14, 2021
Légèrement au-dessus pour @marquinhos_m5 💥#PSGFCN pic.twitter.com/GwlvN18Fwx
Lafont's counterpart, Keylor Navas, also earned his corn. The Costa Rica international - so effective in the midweek clash against Barcelona in the Champions League - parried Ludovic Blas's shot from just in front of the goal.
Lafont though was the busier of the duo. The 22-year-old pushed Rafinha's shot over the bar and stuck a leg out to thwart Kylian Mbappé's shot.
But Julian Draxler eventually found a way past him on the stroke of half-time.
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Nantes drew level soon after the restart thanks to a defensive blunder from Mbappé.
Kolo Muani intercepted his cross-field pass and strode on to thrash past Navas.
Ten minutes later goalscorer turned provider. After leading the counter, Kolo Muani surged into the PSG penalty area and unselfishly slid the ball across the goal for Moses Simon to stab home.
Nantes, led by the former PSG boss Antoine Kombouaré, dug in for the at win that took them up a place to 18th and to within one point of safety.
"We had a good first-half but in the second, we put less intensity," PSG midfielder Danilo told Canal Plus.
"It's hard to analyse what happened. We could have gone top but we didn't win. We are disappointed but there are still some important matches to play."
At the top of the Ligue 1 food chain, Lille lead the way on 63 points with PSG and Lyon separated by goal difference on 60 points. Monaco are seven points off the lead in fourth.
