Mali Hingani's try in the last move of the match snatched a dramatic 32-29 win for La Rochelle over French and European champions Toulon.
The 23-year-old - one of four try scorers for the hosts - produced a delightful pivot to go over and touch down, with Peter Grant adding the extras to ease his side’s relegation fears.
Toulon remain top of the table however, with second-placed Clermont Auvergne - their opponents in the Champions Cup final - also upset, beaten 31-10 at relegation-threatened Castres.
Toulon made 14 changes to the team that defeated Leinster in last weekend’s Champions Cup semi-final, with only Frederic Michalak retaining his place in the starting line-up.
The mercurial fly-half, who was replaced early in the second half after an ineffective performance against Leinster, did his chances of featuring in next weekend’s final no harm by scoring 19 points.
La Rochelle went ahead with a splendid fourth-minute try by Alofa Alofa, who chipped over the Toulon defence and ran on to touch down, with Fabien Fortassin converting.
However, Toulon struck back immediately, stretching the La Rochelle defence before Josua Tuisova went over in the corner.
A pulsating encounter then saw 39-year-old veteran Sireli Bobo display all his experience in seeing a gap and bursting through to touch down under the posts for his 50th try in elite French rugby - Fortassin converting.
Mamuka Gorgodze went over for Toulon's second try, Michalak adding the extras for a 20-14 lead, but the hosts hit back when impressive teenage centre Elliott Roudil put a grubber kick in behind the visitors' defence and Kini Murimurivalu had the legs to get to the ball first and touch down.
The hosts were denied a try five minutes from the break when scrum-half Julien Audy went over, but a Fortassin penalty gave them a 22-20 advantage at the interval.
Toulon regained the lead through two Michalak penalties, and the Frenchman than cancelled out a Grant three-pointer, but that was not enough as the indefatigable hosts stole it at the death through Hingani's try.
Clermont crushed by Castres
Toulon’s Champions Cup final opponents Clermont Auvergne also crashed to an away defeat as they lost 31-10 to relegation-haunted Castres.
Castres ran in five tries, with winger Remy Grosso grabbing a hat-trick in the bonus point win.
Former All Black Sitiveni Sivivatu and prop Yannick Forestier also crossed for the 2013 champions, whose margin of victory could have been greater had Rory Kockott not missed four kicks at goal.
Grosso's second try was a gem, set up by two spectacular off-loads from Remi Lamesat and Thomas Combezou.
"In my team, honestly, there are players who deserve to be at the World Cup -- Lamerat, Remi Tales, Kockott and Grosso," said Castres coach Mauricio Reggiardo.
Second-bottom Castres are level with Bayonne on 47 points, while Brive and Grenoble are a point further ahead as the relegation dogfight looks destined for a thrilling conclusion.
Bayonne improved their survival hopes with a 42-33 win over Grenoble with South African-born French international full-back Scott Spedding scoring three of his team's six tries.
Rock-bottom Lyon were effectively relegated after losing 37-22 at home to Bordeaux while Oyonnax boosted their play-off hopes with a 21-16 win over Racing Metro.
Oyonnax had stunned Clermont 11-10 last time out and on Saturday were indebted to Argentine fly-half Benjamin Urdapilleta, who kicked all of their points.