Aston Villa have recalled O'Rielly from his loan with Shrewsbury Town and placed him with MK Dons for the remainder of the season.
"I’m buzzing to be here," O'Reilly said of his Dons move. "I’m happy it’s finally got over the line and I can’t wait to get started. The stadium is great, it’s a big pitch too and I’m excited to show people what I can do.
"I’m a creative player. I like to get on the ball a lot, I like to excite fans and play with no fear. I want to help the team as much as I can, I want to create chances and score goals. I want to make an impact and be positive around the group."
Dons manager Scott Lindsey said: "Tommi is a really exciting footballer. He plays as a number ten, but can fulfil a position anywhere across that frontline. He's really comfortable on the ball, likes to dribble, drive forward and make things happen.
"He's a player that I think we needed, we haven't got many ball carriers in the squad and he certainly brings that.
"He's had a good loan spell at Shrewsbury Town in League One, that was a really good experience for him and he's ticked that box but now he can come to a team that's fighting for promotion."