Andy Murray will coach his long-time former rival Novak Djokovic at the Australian Open in 2025.
Britain's three-time Grand Slam champion Murray retired from tennis in August after a 19-year career.
The pair will work together in the off-season and in the build-up to the Australian Open, which takes place from 12-26 January.
Former world number one Murray said he was "looking forward to spending time on the same side of the net as Novak for a change".
Djokovic has won the Australian Open a record 10 times, including beating Murray in four finals.
He and Djokovic had a number of memorable meetings during his career, with Murray beating the Serb to win two of his major titles.
Djokovic posted a video on X of clips of the two, jokingly titled: "He never liked retirement anyway."
"We played each other since we were boys, 25 years of being rivals, of pushing each other beyond our limits," the 24-time Grand Slam champion said.
"We had some of the most epic battles in our sport. I thought our story may be over, - turns out it has one final chapter.
"It's time for one of my toughest opponents to step into my corner."