The latest twist in his injury saga was confirmed on Saturday night and he is set to go under the knife later this week. O'Connell has not played since October.
The Munster lock missed Ireland's summer tour to New Zealand with a knee injury and then pulled out of the Autumn internationals when his long-standing back problem flared up again.
A statement from Munster said: "Following consultation between IRFU and Munster medical staff and the player himself, it has been decided that Paul O'Connell will undergo back surgery at the earliest opportunity."
Early estimates for recovery from the operation have been set at two months, ruling out any hopes O'Connell had of playing for Ireland in the 2013 RBS Six Nations. If that is a correct time-frame, and he can regain full match fitness and play for Munster before the end of the season, he could still come into contention for a third tour with the British & Irish.
"I think it this is a really massive step forward because the uncertainty for Paul has been a frustration. He has been beavering away with a whole lot of medical support and it has been, what they would term, a conservative management of his injury," Munster head coach Rob Penney told the Limerick Leader.
"They have come to the conclusion that the time has now come to be more on the front foot, to be more aggressive with the treatment. The good thing is there is light at the end of the tunnel for the guy and whatever happens, let's just hope that he has got full use of his faculties and everything so he can live a normal and healthy life - the rugby stuff is secondary."