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.
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".
The pair will work together in the off-season and in the build-up to the Australian Open, which takes place 12-26 January.
This will be Murray's first coaching role since retiring from playing.
Djokovic, a 24-time Grand Slam champion, has won the Australian Open a record 10 times and beat Murray in four finals in Melbourne.
The Serb 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," Djokovic 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."
Djokovic 'looking forward to having Murray by my side'
Djokovic is level with Margaret Court for the most major singles titles by any player.
It would be fitting for him to overtake the Australian legend in Melbourne, where he has enjoyed huge success over the years, but he had a difficult 2024 by his high standards.
Djokovic did not win a major title for the first time since 2017, beaten in the Australian Open semi-finals by world number one Jannik Sinner before losing to Carlos Alcaraz in the Wimbledon final.
He did, however, clinch a long-awaited Olympic gold in Paris - something he described as his "greatest achievement".
Murray and Djokovic have maintained a good friendship throughout their years on tour, having been born just weeks apart and grown up as junior rivals.
Djokovic leads the head-to-head 25-11 but Murray claimed memorable victories over him to win the US Open in 2012 and Wimbledon a year later.
He did, however, lose to Djokovic in the Melbourne showpiece in 2011, 2013, 2015 and 2016, and also lost the French Open final in 2016.
Murray replaced Djokovic as world number one at the end of the 2016 season, going on a 24-match winning streak to end the year, but a hip injury a year later would ultimately impact his career.
Murray announced in the summer that the Paris Olympics would be his last tournament, and he made it to the quarter-finals of the men's doubles alongside Dan Evans before bowing out.
"I'm going to be joining Novak's team in the off-season, helping him to prepare for the Australian Open," Murray said.
"I’m really excited for it and looking forward to spending time on the same side of the net as Novak for a change, helping him to achieve his goals."
Djokovic made changes to his team this year, including parting ways with long-time coach Goran Ivanisevic.
The Olympic medal was the only title he won in 2024 and he ended his season early after sustaining an unspecified injury.
It is the first season since 2005 in which he has not won an ATP event, and only the fourth since 2008 in which he has not won one of the four Grand Slam titles.
"I look forward to starting the season with Andy and having him by my side in Melbourne, where we've shared many exceptional moments throughout our careers," Djokovic added.
BBC