Australian international flyhalf Christian Lealiifano has agreed to join Ulster on a five-month deal.
Lealiifano's contract will run until 22 January, following the conclusion of the Champions Cup pool stages.
He will then return to the Brumbies for the start of the Super Rugby season.
The Auckland-born star made his debut for the Canberra-based franchise back in 2008 and earned his first international cap in the 2013 Test series against the British and Irish Lions.
He has played 19 times for the Wallabies, with his last appearance coming against England in June last year.The 29-year-old was diagnosed with leukaemia 12 months ago and he has since undertaken the necessary treatment.
He made a remarkable return to action for the Brumbies in June, having been named as co-captain by head coach Stephen Larkham.
Lealiifano said: "I'd like to thank the Brumbies for allowing me to do this stint abroad. I'm really excited to be joining up with Ulster Rugby and I'm looking forward to getting out there in front of the supporters at Kingspan Stadium.
"I can't wait to experience the rugby and the culture in Belfast."
Ulster director of rugby Less Kiss is delighted to welcome Lealiifano on board: "This is a massive boost for us as we approach the start of the season. It was paramount that we signed an experienced player to give us another option at flyhalf and this is a fantastic solution for us.
"Christian has the playing talent, the leadership ability and the personality to make a big impact here. He has overcome significant challenges in his career and that is testament to his bravery and strong character.
"He's a proven leader and we're excited by the influence that he'll have on our young flyhalves Peter Nelson, Brett Herron, Johnny McPhillips and Callum Smith.
"We also have two exciting players in our Academy, Michael Lowry and Angus Curtis, who will also have a fantastic opportunity to learn from Christian.
"From speaking to Christian, I know that he is very excited by the challenge and is looking forward to joining up with us soon."
Lealiifano's short-term contract coincides with Paddy Jackson's absence from the province's squad. The Ireland and Ulster fly-half, along with team-mate Stuart Olding, has been stood down from rugby duties as he awaits trial on rape charges.
Jackson, Olding and fellow players Blane McIlroy and Rory Harrison are facing charges in Laganside Magistrates' Court on Wednesday.
