O'Donnell made his Munster debut as a 20-year-old against Scarlets in Musgrave Park in 2007 and has established himself as a key member of the current squad. It was against the same Welsh side that he made his first Heineken Cup appearance in December 2011 in Thomond Park.
The flanker's great form last season was rewarded in the summer as he won his first two Ireland caps on the tour of North America, and he was named the 2012/13 Munster Rugby Player of the Year.
O'Donnell has been out of action since September after injuring his knee against Zebre but Head Coach Rob Penney revealed last week that O'Donnell is one week ahead of schedule in his recovery and should be back to full training in December.
Tommy had the following to say after committing to the province until June 2016: "This is where I want to be and I enjoy playing my rugby here. I know it hasn't been the best of starts to the season for me with injury, but like last year I just want to come back fighting and push on to the next level again."
Head Coach Rob Penney added, "Tommy is a great dynamic player and a huge asset to any side so we are particularly pleased that he has committed to Munster for another two years."