Florian Denos got the hosts up and running with a third minute try before the game descended into a mini-battle between the sides’ respective kickers.
It looked as though Toulon would reverse the deficit when Delon Armitage went over and two home players were sin-binned, Scott Newlands and Valentin Ursache, but Oyannox held on before Urdapilleta’s heroics at the death.
And there was another surprise at the Stade Aime Giral as Toulouse fell to Perpignan 20-16.
Sofiane Guitoune’s early try steadied the Perpignan nerves and James Hook kicked consistently as they secured an upset to climb into the top half of the table.
Elsewhere there were wins for Bayonne and Castres whilst Grenoble and Brive played out a tight 12-12 draw.
On Friday, table-toppers Stade Francais beat rivals Montpellier 18-11 at Stade Jean Bouin although the hosts were far more dominant than the scoreline suggested.
Prop Rabah Slimani opened the scoring with Julien Dupu kicking the conversion and two further penalties to strengthen Stade Francais' position.
Jules Plisson added their second try after the restart but Montpellier set up a nervy finish when fly-half Francois Trinh-Duc went over.
The weekend's final match saw Clermont Auvergne crush Bordeaux-Begles 40-11 on Sunday to move into second place - a game that will largely be remembered for the amount of yellow cards dished out.
Seven players were sent to the sin bins in total, leaving Bordeaux with just 12 men of the pitch at one stage, as Clermont ran riot with a host of tries.
- Sports & Recreation
- Scott Newlands