Bath's European Champions Cup quarter-final hopes suffered a crushing setback as the Scarlets cut them to shreds at the Recreation Ground.
The Welsh team's spectacular 35-17 bonus-point victory sets them up for a potential Pool Five decider against three-time European champions Toulon next weekend.
Bath, though, are facing being frozen out of the last-eight picture after their red-hot opponents ran in tries by lock Tadhg Beirne, wing Paul Asquith and Wales international centres Scott Williams and Hadleigh Parkes.
Fly-half Dan Jones added 15 points from the boot as Scarlets made light of losing injured Wales star Leigh Halfpenny 24 hours before kick-off, with outclassed Bath managing tries from wing Matt Banahan and number eight Zach Mercer, plus two Freddie Burns conversions and a penalty.
England head coach Eddie Jones looked on as the 1998 European champions came horribly unstuck, but Bath could have no complaints on a night when the Scarlets dominated every key area.
They moved top of their group, and a quarter-final place will be secured if they see off Toulon at Parc-y-Scarlets in eight days' time.
Bath dominated initial territory, but they suffered a major injury blow when their Wales international fly-half and former Scarlets number 10 Rhys Priestland limped off.
Priestland, who kicked all of Bath's points when they beat the Scarlets in west Wales three months ago, departed just four minutes into the contest and was replaced by Burns.
And Bath were behind their posts just eight minutes later, left reeling by a stunning Scarlets attack that full-back Rhys Patchell started inside his own 22.
Parkes and flanker Aaron Shingler played prominent roles to set up Beirne, who side-stepped England star Anthony Watson before claiming a memorable try.
Jones added the conversion as Scarlets served immediate notice of their renowned attacking prowess that drove them to last season's Guinness PRO12 title.
England flanker Sam Underhill, making his first appearance for two months following prolonged concussion symptoms, was prominent in Bath's attempts to wipe out the deficit, before Burns opened their account through a 22nd-minute penalty.
Scarlets number eight John Barclay's penalty indiscretion -- he roamed offside to halt Bath scrum-half Chris Cook just two metres from his own line -- gave referee Jerome Garces little option but to sin-bin him.
But the Scarlets were untroubled by his departure, rocking Bath on their heels again as they claimed a second try when Patchell moved possession wide, Parkes acted as the link and Asquith crossed unopposed in the corner.
Bath did not know what had hit them, and it got worse nine minutes before half-time -- and with Barclay still off -- when scrum-half Gareth Davies sprinted through a huge gap following an attacking Scarlets lineout and support runner Parkes finished off between the posts.
Jones' conversion made it 19-3 and the fly-half then kicked a penalty following a Bath scrummaging offence, with the home side trooping off at half-time after being taught a lesson in terms of ambition, creativity and running rugby.
Williams claimed Scarlets' fourth try 11 minutes into the second period, collecting Patchell's cleverly placed kick to score, and although Banahan's acrobatic catch and finish for a touchdown that Burns converted cut Bath's arrears to 19 points, they were still way off the pace.
Another Jones penalty took the Scarlets past 30 points and, despite Bath belatedly stirring through Mercer's touchdown, it was a case of way too little, too late as the Welsh side comfortably closed out a comprehensive success.
