Wales failed to secure a Grand Slam for the second time in three years when France's Brice Dulan scored a late try to give the home side a 32-30 win.
Fullback Dulin dived over as France completed a remarkable turnaround to give Les Bleus the win and a bonus point that leaves them needing to beat Scotland on Friday with a bonus point and make up a 20-point deficit to top the standings.
Should they win by 20 points at the Stade de France, the championship would be decided on tries scored - Wales have 20 to France's 15 so far.
Women's Six Nations Championship
Griggs wants more despite huge Ireland victory
11/04/2021 AT 15:18
Wales had the game firmly in hand but picked up two yellow cards in the finale and were left exposed to France's late assault, which culminated in Dulin's try after Charles Ollivon had reduced the arrears.
Wales, who lead the table with 20 points ahead of France in third place on 15, were 30-20 up after tries by Josh Navidi, Josh Adams and Dan Biggar - who kicked the rest of the points - and France were a man down after Paul Willemse was sent off for an eye gouge, but things went pear shaped from there.
Taulupe Faletau picked up a yellow card for repeated infringements in the 72nd minute and he was followed into the sin bin by Liam Williams one minute later.
With the field wide open, Fabien Galthie's side piled on the pressure and Ollivon powered past the whitewash with three minutes left.
Romain Ntamack converted before Dulin, on the left flank, touched down in the corner two minutes into dead time to send the French players into raptures.
After a sterling start to the championship with three victories, France narrowly lost to England last weekend and they looked shaky in defence in the first half, leaving Wales in control of a game long delayed by numerous TMO reviews.
Romain Taofifenua picked the ball from a ruck after Gregory Alldritt had been stopped just before the line and touched down to reward France for their early domination.
Wales hit back as Biggar found a line past Julien Marchand, converting the try to put the visitors level.
But there was more brilliance for France with Antoine Dupont going over after being set up by Jalibert who had collected Dulin's chip over the Wales defence.
Wales stretched the French defence during a long possession spell, which ended with Navidi scoring the fourth try of the game after only 18 minutes.
France, who already had Taofifenua out injured early on, were forced to replace flyhalf Matthieu Jalibert by Ntamack after taking a knock while attempting a tackle.
Adams, whose try was awarded following a lengthy TMO review after it appeared that he had been held up, opened a potentially decisive gap as France looked out of sorts.
Wales thought they had a bonus in the bag when Louis Rees-Zammit touched down in the corner, only for the try to be ruled out as the winger was millimetres out.
Les Bleus lost the plot after a Dulin try was cancelled and turned into Willemse's red card, but Wales were even less composed, letting a promised Grand Slam slip from their hands in the dying seconds of a memorable test.
Six Nations
Wales crowned Six Nations champions as Scotland beat France
26/03/2021 AT 22:08
Six Nations
France's Dupont set to miss Scotland game after positive Covid-19 test
19/02/2021 AT 18:12