Bayonne shock Toulon
The south-west club returned to the top flight at the first time of asking by finishing second in the Pro D2 last season, and they held off a late Toulon fightback to kick off their campaign in style.
"We're a little surprised to win," said Bayonne coach Vincent Etcheto.
"We will savour it. We did not know how they would play, and we didn't know our level either. Maybe we still don't and there's still 25 games to go.
"But maybe we will take a picture of the table."
It is the second season in a row that Toulon, the 2014 champions, have lost on the opening weekend.
"We did not deserve to win," admitted Toulon boss Diego Dominguez.
"The players made too many mistakes, there were too many lost balls. I'm annoyed because that was a game we could have won by being smart."
Fullback Martin Bustos Moyano kicked a third-minute penalty to put the hosts in front, and after his opposite number Leigh Halfpenny kicked six points for Toulon, Bayonne hooker Gregory Arganese burrowed over for the game's first try.
Bustos Moyano added the extras, and wing Romain Martial then kicked a long penalty to extend Bayonne's lead to seven points.
But Toulon flank Charles Ollivon, who left Bayonne last year, grabbed his team's first try of the season just before half-time, and the following conversion from Welshman Halfpenny levelled the scores at 13-13 at the interval.
South African fly-half Willie du Plessis slotted over a penalty to put Bayonne back in front, before Arganese powered over again with Du Plessis' conversion putting Etcheto's men firmly in control.
Halfpenny added another penalty, but Jean Monribot touched down for Bayonne's third try to leave Toulon, who lost to Racing 92 in last season's Top 14 final, 12 points behind with a quarter of an hour to play.
French international lock Romain Taofifenua's try for Toulon coupled with Halfpenny's conversion made for a tense final eight minutes, but Bayonne held on to a fantastic victory.
On Saturday, Racing 92 started their title defence with a 15-9 loss at Bordeaux-Begles, while Clermont had to settle for a dramatic 30-30 draw at La Rochelle.
The opening day also saw wins for Stade Francais, Castres and Toulouse.
Top 14 results:
Bayonne 28 Toulon 23
Bordeaux-Begles 15 Racing 92 9
Castres 28 Pau 11
La Rochelle 30 Clermont 30
Lyon 15 Brive 15
Stade Francais 54 Grenoble 20
Toulouse 20 Montpellier 12
Top 14 table (played, won, drawn, lost, points for, points against, bonus points, total points):
Stade Francais 1 1 0 0 54 20 1 5
Castres 1 1 0 0 28 11 0 4
Toulouse 1 1 0 0 20 12 0 4
Bordeaux 1 1 0 0 15 9 0 4
Bayonne 1 1 0 0 28 23 0 4
Clermont 1 0 1 0 30 30 0 2
La Rochelle 1 0 1 0 30 30 0 2
Lyon 1 0 1 0 15 15 0 2
Brive 1 0 1 0 15 15 0 2
Toulon 1 0 0 1 23 28 1 1
Racing 92 1 0 0 1 9 15 0 0
Montpellier 1 0 0 1 12 20 0 0
Pau 1 0 0 1 11 28 0 0
Grenoble 1 0 0 1 20 54 0 0
Agence France-Presse
