The Irish province became the first side to advance to the semi-finals of the Celtic Cup after recording a shock win at Stradey Park.
CELTIC CUP QUARTER-FINAL
Scarlets (5) 12
Tries: S Finau, D Burn. Con: G Bowen.
Connacht (5) 14
Try: M McHugh. Pens: McHugh (3).
Full-back Mark McHugh was the star of the show, a try and three penalties providing all the visitors' points.
The Scarlets managed two tries from Salesi Finau and Dale Burn, but were let down by Gareth Bowen's poor kicking.
The fly-half failed with two penalties and a drop-goal in the closing five minutes that could have snatched the win away from the deserving Irish and preserved the Scarlets' 100% record.
Connacht started brightly on their first visit to Llanelli, a clean break from outstanding centre Darren Yapp threatening
the home line.
The Scarlets pressure soon built, though, and a Connacht mistake paved the way for the opening score.
Fly-half David Hewitt sent a drop-out 22 directly into touch, and from the resulting scrum the home side fired the ball
straight out to Finau on the left wing.
The powerful Tongan used his strength to blast through the high challenge of Matt Mostyn and claim a try in the corner.
The Irish province drew level when the Scarlets delayed at the base of a ruck, allowing the visitors to steal Burn's
laboured pass to Bowen.
With the defence on the back foot, Connacht quickly spun the ball wide, allowing McHugh over for the
Much to the chagrin of the expectant Llanelli crowd, the visitors continued to show no respect to Stradey's formidable
reputation, disrupting the home side up front and breaking the line behind.
With half-time approaching, Connacht battered at the home line, prop Ray Hogan being held up in the in-goal area before Yapp
knocked on with the whitewash at his mercy.
Bowen had a chance to settle Scarlet nerves early in the second half when a forceful Finau break led to a penalty shot at
goal, but the fly-half sent his kick wide.
The Irish blasted back at the home line, before a moment of indiscipline from wing Conor McPhillips cost them dear.
He was yellow carded for a late tackle on Matthew Watkins, the penalty was kicked to touch and from the line-out Burn
sniped over for a fine converted try.
Connacht struck straight back with a penalty, but it could have been more, an awkward bounce from a grubber kick seeing
McHugh blow a certain five-pointer.
McHugh's second penalty brought the visitors back to within a point with just 10 minutes to go, as the Scarlets began to
wobble under the relentless pressure.
Another careless penalty was conceded smack in front of the home posts, and McHugh made no mistake with the simple kick to
give the Irish the lead for the first time.
Bowen missed with a long-range shot at goal, but the Scarlets were fighting back furiously with time running out.
Connacht were tempted offside, giving Bowen an 82nd-minute shot at goal from in front of the posts -
but the fly-half slid his kick wide and failed with a final desperate drop-goal to send the north-west of Ireland into raptures.
"We knew how tough it would be over here, but we stuck at it and got the win we came for," said man-of-the-match McHugh.
"We've had a few good wins and now we're looking forward to the semi-final."
Scarlets centre Matthew Watkins was philosophical in defeat.
"They are a good side who have done well away from home," said Watkins, "They took our set-piece game away from us and we couldn't play our game - we've got no complaints."
Scarlets: Barry Davies; Tal Selley, Matthew Watkins, Leigh Davies (capt), Salesi Finau; Gareth Bowen, Dale Burn; Phil John, Rhys Williams, John Davies, Bryn Griffiths, Adam Jones, Vernon Cooper, Ian Boobyer, Emyr Lewis.
Replacements: David Maddocks, Adam Yelland, Gavin Quinnell, Gareth Williams, Mike Phillips, Ceiron Thomas, Richard Rees.
Connacht: M McHugh; M Mostyn, D Yapp, T Allnutt, C McPhillips; D Hewitt, M Walls; R Hogan, B Jackman, B Boiroux, D Browne, A Farley, P Neville, T Carter, J O'Sullivan.
Replacements: J Fogarty, A Clarke, M McCarthy, M Lacey, C Keane, Shane Moore, T Robinson.
Referee: Gregg Davies (Scotland)