The Gnoll, Neath.
Captain Barry Williams and flanker James Bater also scored as the Ospreys won a feisty west Wales derby over their local rivals with room to spare. The victory takes the Ospreys five-points ahead of Irish giants Munster - who face Connacht on Monday - and spells the end of the Scarlets's reign as Celtic League champions.
The Scarlets had hoped that the return of British Lions hooker Robin McBryde, Amercian Dave Hodges and the arrival of ex-All Black prop Dave Hewett would provide a stern test for the Ospreys up front. As it turned out, McBryde and Hodges both left the field injured while Hewett was given a painful lesson in the scrums from local boy Duncan Jones.
A typically tight derby encounter finally exploded into life just before the break. Scarlets drew first blood when youngster Jon Mills popped out of a ruck to score a surprise try in the corner only for a moment of brilliance from Williams saw the Ospreys take a lead again. Williams sped around and through four would-be tacklers before the ball passed through several forwards ending with Barry Williams scoring in the corner.
Shane Williams then scored himself just 85 seconds into the second half when he sped past Gareth Bowen to send the Ospreys on their way. Bater then crashed over before Williams danced through for his second - moments after Chris Wyatt was sent to the sin - to end an emphatic display.
Ospreys: A Durston; E Seveali'i, S Parker (D Tiueti, 80), G Henson, S Williams; M Jones (D Bishop, 67), J Spice (R Rees, 74); D Jones, B Williams (capt, R Hibbard, 76), A Millward (A Jones, 63), B Cockbain, J Thomas (A Newman, 74), J Bater, R Jones (A Lloyd, 70), R Pugh (A Jones, 16-25)
Tries: S Williams (2), B Williams, J Bater
Con: M Jones Pens: G Henson (2)
Scarlets: G Evans (capt); T Selley, M Watkins, S Finau, A Havili; G Bowen (A Thomas, 21-32), D Peel (M Phillips, 74); P John, R McBryde (M Rees, 50), D Hewett (J Davies, 73), V Cooper, C Wyatt (B Griffiths, 74), D Hodges (A Powell, 29), D Jones, J Mills
Tries: J Mills
Cons: G Bowen
Referee: N Whitehouse