The Scarlets marked Jonathan Davies' return to action with an 18-13 PRO12 victory over high-flying Munster at Parc y Scarlets.
Both teams headed into the game in good form. Scarlets had overcome Edinburgh on their last outing, while Munster were seeking to make it a Welsh double following last week's win over Ospreys.
But the Welsh hosts muscled up for 80 minutes and were deserving of their narrow victory.
The two teams swapped penalties around the 15-minute mark, before Scarlets crossed for the game's first try on 27 minutes, when Gareth Davies broke through the line. But the conversion was missed, and minutes before half-time the visitors were able to overturn the deficit.
Gerhard Van Den Heever crossed for Ian Keatley to convert, and Keatley added a penalty goal shortly after to make it 13-8 to Munster at the break.
But a flurry of points in a frantic two-minute period around the 50-minute mark turned the contest on its head. Aled Thomas booted over a penalty before John Barclay intercepted the ball and raced away for a superb individual score.
Thomas added the conversion, and despite an avalanche of pressure from the visitors in the minutes that followed, compounded by the sin-binning of Josh Turnbull on 67 minutes, Scarlets were able hold their line intact to see out an important win.
It was a huge win for Scarlets, breathing further life into their play-off hopes, while the result inflicts a sizeable dent in Munster's own hopes of finishing top of the table.
Tries: G Davies, Barclay
Pens: Barkley, Thomas
Try: van der Heever
Pens: Keatley 2
Scarlets: 15 Jordan Williams, 14 Kristian Phillips, 13 Jonathan Davies, 12 Olly Barkley, 11 Frazier Climo, 10 Aled Thomas, 9 Gareth Davies, 8 Rob McCusker (c), 7 John Barclay, 6 Josh Turnbull, 5 Johan Snyman, 4 George Earle, 3 Samson Lee, 2 Emyr Phillips, 1 Phil John
Replacements: 16 Kirby Myhill, 17 Rob Evans, 18 Jacobie Adriaanse, 19 Richard Kelly, 20 Sione Timani, 21 Rhodri Williams, 22 Gareth Maule, 23 Adam Warren
Munster: 15 Simon Zebo, 14 Gerhard van den Heever, 13 Casey Laulala, 12 Denis Hurley, 11 Johne Murphy, 10 Ian Keatley, 9 Duncan Williams, 8 James Coughlan (c), 7 Tommy O'Donnell, 6 CJ Stander, 5 Donnacha Ryan, 4 Donncha O'Callaghan, 3 Stephen Archer, 2 Duncan Casey, 1 Dave Kilcoyne
Replacements: 16 Ger Slattery, 17 James Cronin, 18 BJ Botha, 19 Dave Foley, 20 Sean Dougall, 21 Gerry Hurley, 22 JJ Hanrahan, 23 Ronan O'Mahony.
Referee: Dudley Phillips (Ireland)
Assistant Referees: Wayne Davies, Rhys Thomas (both WRU)
Citing Commissioner: Gwyn Bowden (WRU)
TMO: Tim Hayes (WRU)