The Scarlets served up a Boxing Day special to claim their biggest ever victory over the Ospreys in front of a packed Parc y Scarlets.
The home side sizzled throughout, scoring six tries in a dominant 44-0 win.
Wings Ryan Conbeer and Steff Evans touched down for two apiece, while replacement Kieran Hardy and flanker Josh Macleod also crossed.
Leigh Halfpenny put in another imperious display, kicking 12 points, but it was fly-half Angus O’Brien who picked up a successive man-of-the-match award, with assists for five out of the six tries.
In front of a crowd of 13,682, the Scarlets took early control, bossing possession and territory.
The Ospreys defence was proving stubborn early on, but it was Halfpenny who broke the deadlock with a penalty on 18 minutes.
Six minutes later the home crowd were on their feet to celebrate a superb opening score by wing Evans.
It came via a couple of smart inside passes from O’Brien and Aaron Shingler with Evans doing the rest to race over under the posts.
Halfpenny converted then added another penalty as the Scarlets maintained their grip on the match.
Then in the final moment of the half, the Scarlets had a second try.
Another threatening attack had the Ospreys on the back foot, the ball was recycled and it was O’Brien again who put in a beautifully-weighted cross-field kick into the path of Conbeer.
The young winger still had plenty to to do, but he pouched the ball at pace and raced clear of the defence to score.
Halfpenny added another successful kick and the Scarlets were 20-0 up at the break.
Despite the rain getting heavier for the second period, there was no stopping the Scarlets’ relentless pursuit of victory.
Blade Thomson and Sam Lousi were at the heart of the forward effort, while Macleod was at his scavenging best at the breakdown.
After Luke Morgan was shown yellow for a high tackle on Conbeer, the wing claimed his second before Evans gathered a bouncing ball for the bonus-point score.
With the Scarlets oozing confidence, replacement Kieran Hardy sniped blindside, then Macleod added try number six, taking a clever pass from Ryan Lamb to dive over in the same corner as his match-winning try in the same fixture two years ago.
The Scarlets thought they had a seventh late on, only for a length-of-the-field score from Hardy to be chalked off by the officials for a late hit earlier in the movement.
In the closing minutes Jake Ball and Werner Kruger were both shown yellow, but the 13-man Scarlets were able to hold out to nil their rivals for the first time.
Scarlets - tries: S. Evans (2), R. Conbeer (2), K. Hardy, J. Macleod. Cons: L. Halfpenny (3), A. O’Brien. Pens: Halfpenny (2).