Dan Biggar kicked all the Ospreys points but it took a resilient defence to clinch a first Welsh win at Thomond Park in six years.
Ronan O’Gara had an off day with the boot but his late try set up a grandstand finish only for the Ospreys to hold out.
The result lifts the Ospreys above Glasgow to second in the race for home advantage in the play-offs.
It also means Cardiff Blues could yet pinch a place in the end-of-season mix if they defeat Munster on the final day.
There was nothing to separate these teams in the table before kick-off, level on points, wins and even tries. However both were pushing hard to secure their place in the Magners League play-offs and the chance of home advantage in the semi-final.
O’Gara kicked Munster into an early lead with a tenth-minute penalty as the home pack pressed in the set-pieces.
But the Ospreys defence was on the mark, Jerry Collins saving what looked a certain try with his tackle on Paul Warwick.
O’Gara hit the post and pushed another effort wide either side of Biggar’s first successful attempt and the young Welshman struck again to hand the Ospreys a 6-3 lead at half-time.
Biggar rapidly extended that to 15-3 with three quick-fire penalties in the space of ten minutes after the break as the Ospreys stepped on the gas. The third penalty saw Munster No8 James Coughlan sent to the sin bin.
However Munster used their wealth of experience to ride the ten-minute spell and after O’Gara kicked a second, Ospreys captain Ryan Jones was shown a yellow card for a professional foul.
Three minutes later and O’Gara hauled Munster back into the game when he slipped through a crowd of players to touch down, ten minutes from time.
However he missed the conversion and the Ospreys held out for an impressive win.
