The Scarlets secured a European Champions Cup quarter-final place as Pool 5 winners after toppling Toulon 30-27 in west Wales.
Tries before the interval by wing Tom Prydie, centre Hadleigh Parkes and fly-half Dan Jones underpinned a stylish Scarlets success, with Jones adding three conversions and two penalties, and Rhys Patchell a long-range penalty.
It ended a six-year wait for Welsh representation in the knockout stage of European club rugby's blue riband tournament, while the Scarlets went through for a first time since 2007.
Three-time European champions Toulon still progress as one of three best runners-up following tries from Duane Vermeulen and Chris Ashton, plus fly-half Anthony Belleau's 11-point haul and two Francois Trinh-Duc penalties that pushed Scarlets to the wire and ensured a priceless losing bonus point.
Toulon will be away in the last-eight, while the Scarlets' hopes of a home tie depend on the outcome of Sunday's closing group fixtures.
The game began at a furious tempo and both teams had a try on the scoreboard within six minutes.
Scarlets, continuing from where they left off against Bath eight days ago, were immediately into their stride and went through phase-play impressively before Patchell fired out a long pas to Prydie, who crossed unopposed.
Jones added the conversion, but Toulon prospered from the restart when their opponents failed to gather an innocuous kick-off, conceded a lineout and Vermeulen powered through unopposed for a soft try.
Jones then kicked a penalty to open up a five-point lead, yet it proved short-lived as Toulon hit back through a classic opportunist score from Ashton.
The former England wing intercepted Patchell's pass, and then set off on a 65-metre run when he showcased his blistering pace to claim a try that Belleau converted.
But the Scarlets were back ahead just two minutes later after their Wales flanker Aaron Shingler charged down Belleau's attempted clearance, kicked the ball on and Parkes gathered to finish in the corner.
Jones' touchline conversion, followed by him and Belleau exchanging penalties, meant the Scarlets led 20-18 after just 27 minutes as the points extravaganza continued.
And they did not stop there, as their third try arrived after a sharp break by wing Paul Asquith, and even though he was stopped short of Toulon's line, a supporting Jones finished off by touching down between the posts and then converting.
A first-half of unrelenting pace ended when Belleau completed his penalty hat-trick, and the Scarlets trooped off 27-21 ahead in pursuit of reaching the Champions Cup last-eight.
Patchell then kicked a penalty from just inside the Toulon half, but Scarlets could not break free and substiitute Trinh-Duc booted two penalties during a five-minute spell to set up a pulsating closing quarter.
Toulon established a territorial foothold moving into the closing 10 minutes, yet they were kept at bay, with Trinh-Duc sending a last-gasp drop-goal attempt drifting wide.