Henson, 26, had hoped to regain fitness after sitting out the Welsh region's EDF Energy Cup Final win over Leicester Tigers but has run out of time for the showdown in Cork.
Ospreys physio Chris Towers said: "Gavin is progressing nicely but needs a bit of extra time to be fully fit. We could have rushed him back for this game but we decided against it. But we hope he is ready for action soon."
Henson joins long-term absences Mike Phillips (knee) and Nikki Walker (ankle) as the Ospreys bid to secure Heineken Cup qualification for next season.
Head Coach Lyn Jones still has aspirations as finishing as the highest place Welsh region: "With five games remaining of the season, we are not looking down the table, we are concentrating on the teams currently above us.
"We are seven points behind the Scarlets and twelve points behind the Blues, but we have two games in hand on both of them, and we are still targeting finishing above both of those sides to finish the highest of the Welsh regions.
"It will be a tough ask, and the games will come thick and fast over the final weeks of the season, but we will be taking inspiration from our form at the end of last season, when we came back to the Magners League after the EDF Energy Cup Final and put together a good run of results in tough circumstances to rise up the table and take the title.
"Even though we have to concede that the title is out of reach for us this year, I'll be looking to the players to keep their focus for the next 4/5 weeks as we utilise the whole squad as best as possible as we look to achieve our aim.
"If we are able to finish as the highest placed Welsh side then I think it would be quite an achievement given the disruption our campaign has had due to international call-ups and long term injuries from last season, with us only able to select from a full squad on four occasions in our 13 Magners League fixtures to date.
"Munster may have one eye on their Heineken Cup semi-final next weekend, but it is fair to say that there is never an easy game against Munster as everyone who pulls on the red shirt understands their responsibility. It looks like being a tight affair, something of a battle between the two sides who consistently have the best defences so we know that we will have to be on top of our game."
Munster: Shaun Payne, Brian Carney, Barry Murphy, Kieran Lewis, Anthony Horgan, Paul Warwick, Tomas O'Leary; Federico Pucciariello, Frank Sheahan, Tony Buckley, Mick O'Driscoll, Paul O'Connell (Capt), Donnacha Ryan, Niall Ronan, Denis Leamy
Replacements: Jerry Flannery, Marcus Horan, Anthony Foley, David Wallace, Peter Stringer, Jeremy Manning, Keith Earls
Ospreys: Lee Byrne; Johnny Vaughton, Sonny Parker, Andrew Bishop, Shane Williams; James Hook, Justin Marshall; Duncan Jones, Huw Bennett, Cai Griffiths, Ian Gough, Ian Evans, Jonathan Thomas, Filo Tiatia (Capt), Marty Holah
Replacements: Ed Shervington, Andrew Millward, Lyndon Bateman, Ben Lewis, Gareth Owen, Jonathan Spratt, Aled Brew