Paris - Saint-Etienne moved above arch regional rivals Lyon on goal difference and into Champions League contention on Sunday as they came from behind to inflict more misery on Monaco, beating the beleaguered Principality side 3-2.
Gelson Martins put Monaco into an early lead. Fode Ballo-Toure's own goal on 59 minutes drew Saint Etienne back level, with Remy Cabella and Arnaud Nordin sealing victory, Carlos Vinicius grabbing an injury time consolation for the hapless hosts.
This is dream time for Saint Etienne who despite being France's most decorated side last appeared in the Champions League in 1981.
Lyon can regain third spot as they face second-placed Lille in Sunday's 1900GMT kick-off.
With fifth-placed Montpellier held by Amiens earlier Les Verts are at the very least all but assured of Europa League action next season.
Monaco's 16th loss of a wretched campaign meanwhile left the 2017 champions precariously placed just three points above the relegation zone.
The sight of their Croatian goalkeeper Danijel Subasic hobbling off injured will only have served to deepen the gloom enveloping Leonardo Jardim's side.
Elsewhere, Rennes failed to replicate the heroics of slaying PSG in last weekend's Cup final, and are in danger of finishing out of the top 10 for the first time since 2014 after a 2-2 draw at Toulouse which extended their winless run in Ligue 1 to eight matches.
On Saturday, PSG's dismal run continued as Edinson Cavani missed a stoppage time penalty for the French champions in a scrappy 1-1 home draw with Nice.
PSG retained the league title two weeks ago but they have now won just one of their last six league games as their season continues to disappoint in the aftermath of their nightmare Champions League defeat to Manchester United in March.
They were beaten 3-2 at Montpellier midweek after throwing away a two-goal lead to lose the French Cup on penalties to Rennes, after which star striker Kylian Mbappe was hit with a three-match ban for a rash tackle on Rennes' Damien Da Silva.