Ospreys put another dent in Llanelli Scarlets' fading Celtic League title hopes with a hard-fought derby win.
Ospreys: (19) 25:
Tries: Penalty try.
Pens: Henson 5.
Scarlets: (10) 13:
Pens: Hercus 2.
Gavin Henson starred for the home side as the Wales centre kicked 20 points, including the conversion of a penalty try earned by the Ospreys pack.
In front of a bumper 15,183 crowd at the Liberty Stadium, the Scarlets had an early advantage thanks to Matthew Watkins' interception try.
But the Ospreys held firm, with Jason Spice's cover defence outstanding.
It was sweet revenge for the Ospreys, who only three weeks ago had lost at Stradey Park but showed far more mettle in the return.
It was certainly a better contest, worthy of the large crowd that was a record at the Liberty Stadium in the Celtic League.
Ospreys enjoyed a slender early lead thanks to Henson's drop-goal and penalty, with Mike Hercus opening the Scarlets account with his own penalty kick.
But the visitors soon took the lead thanks to a huge blunder from Matthew Jones that gifted Watkins a breakaway try.
The Ospreys fly-half had neither the wit nor the self-control to hold onto the ball despite the bright red Scarlets shirt loitering in his vision.
Jones ignored a huge gap to run into and instead, on auto-pilot, threw a pass straight into the arms of centre Watkins, who gratefully cantered half the length of the field to dive under the posts.
Hercus slotted the regulation conversion, but two more Henson penalties put the Ospreys back in front just after the half-hour mark.
Then the Ospreys pack, despite conceding more than five stones in weight, produced a huge effort from an attacking five-metre scrum.
The Scarlets eight buckled and referee Nigel Owens awarded a penalty try, with Henson adding the afters for a handy 19-10 lead at the break.
The visitors from Llanelli almost made the perfect start to the second half following a Dafydd James break.
But Alix Popham was just pulled into touch by Ospreys lock Alun Wyn Jones as the Scarlets number eight stretched for the try line.
Hercus and Henson exchanged penalties, before both sides were reduced to 14 men in quick succession.
Scarlets lock Adam Jones was first to be sin-binned for killing the ball, with Ospreys number eight Jon Thomas soon following for the same offence.
But despite the extra space the pace of the game showed on the players in the last quarter, as tired legs failed to make use of the few opportunities created against determined defending.
Ospreys scrum-half Jason Spice:
"It's been pretty lean pickings this year, so we're just happy we put in a performance that got us four points for a start.
"We're going in the right direction, we've been building towards trying to get our season back on track.
"We've been saying that for six months, but there's been a few things we've changed and we're working towards playing a more positive game."
Ospreys: Stefan Terblanche; Damian Karauna, Sonny Parker, Gavin Henson, Richard Mustoe; Matthew Jones, Jason Spice; Duncan Jones (capt), Huw Bennett, Adam Jones, Alun Wyn Jones, Ian Evans, Jonathan Thomas, Steve Tandy, James Bater.
Replacements: Richard Hibbard for Bennett (80), Andrew Millward for A Jones (78), Lyndon Bateman for Evans (80), Andrew Lloyd for Tandy (30), Martin Roberts for Spice (80), Shaun Connor for M Jones (60), Andrew Bishop for Mustoe (77).
Scarlets: Barry Davies; Dafydd James (capt), Matthew Watkins, Regan King, Mark Jones; Mike Hercus, Liam Davies; Phil John, Aled Gravelle, John Davies, Inoke Afeaki, Adam Jones, Dafydd Jones, Gavin Thomas, Alix Popham.
Replacements: Craig Dunlea for J. Davies (43), Matthew Rees for Gravelle (43), Gavin Quinnell for G Thomas (69), Clive Stuart-Smith for L Davies (47), Iestyn Thomas for John (51), Darren Daniels for B. Davies (74). Not Used: Ceiron Thomas.
Referee: Nigel Owens (WRU).