The Ospreys had to rely on the boot of James Hook for all their points, the fly-half kicking seven out of eight penalties as Munster defended fiercely.
The Ospreys started brightly, taking only a minute to gain their first opportunity to earn points, but the normally reliant boot of outside-half James Hook misfired as he sent his penalty wide.
Hook, once again struggling with the boot, should have slotted over a three-point attempt early in the second half but it was quickly forgotten as veteran wing Shane Williams, playing in the final World Cup match of his career, produced a moment of magic in the 49th minute.