The 32-year-old represented the Socceroos 57 times across a 10-year period between 2012 and 2022, scoring seven goals and providing 14 assists, and he appeared at two World Cups in 2018 and 2022.
Mooy made over 360 club appearances for eight different teams across a 15-year professional career, which ended on a historic high with Scottish treble-winners Celtic.
The midfielder was a key cog in Ange Postecoglou's machine that won the Scottish Premiership, Scottish Cup and League Cup in 2022-23, scoring seven goals and registering 11 assists in 42 appearances in all competitions.
Although Mooy still had a year remaining on his contract at Parkhead, the Aussie has decided now is the right time to hang up his boots.
Speaking to Celtic's official website, Mooy said: "While it feels really sad to be leaving the game, I just feel the time is right for me. I have been so fortunate to enjoy such a great career across the last 15 years, creating some fantastic memories.
"I am delighted to finish my career on such a high with Celtic and I would like to thank all the fans for the great support they gave me during the past year - I was delighted to be part of such a memorable season.
"I hope Celtic continue to dominate the game and I wish Brendan [Rodgers], the new manager great success with the great group of lads at the club."
Mooy added: "Playing for my country is something I have loved too and of course I will miss the international set up and so many great people who are involved there.
"I have been fortunate to win a number of caps for my country and this has been really important to me - of course I wish Australia nothing but success for the future and I am sure they can get better and better.
"There are too many people to thank who have played such an important role in my career, so many managers, coaches, staff and fellow players. I have been very privileged to be part of some fantastic football environments, all created by really good people.
"My family is everything to me and I would like to take this opportunity to thank them all for the absolute support I have received from them during my career. I just want to thank them for being there for me in so many ways. Thank you once again to everyone who has supported me right across my career in this great game."
According to The Sydney Morning Herald, Mooy has decided to retire due to a "debilitating back injury" which restricted his involvement for Celtic during the second half of last season.
Born in Sydney, Mooy began his youth career with English side Bolton Wanderers before making 30 appearances for Scottish side St Mirren between 2010 and 2012.
Mooy then returned to his homeland and established himself as a star player in the Australian A-League with Western Sydney Wanderers and Melbourne City; the midfielder won the top-flight title with the former in his first season but he particularly impressed with the latter, winning two Player of the Year awards after scoring 18 goals and provided 14 assists in 53 games.
Mooy left Australia in 2016 and secured a move to Manchester City where he failed to make a single appearance, before enjoying a successful three-year spell wit Huddersfield Town, earning promotion to the Premier League in his first season as a Terrier.
Huddersfield were relegated from the Premier League after two seasons, and after making 120 appearances for the club, Mooy stayed in the English top flight with Brighton & Hove Albion where he featured 32 times in the 2019-20 season.
Mooy then spent two coronavirus-interrupted years in China with Shanghai Port before ending his career on a high with a 12-month spell at Celtic.