The tennis star got the boot Sunday after a 3-judge panel rejected his appeal to stay in the country after Aussie Immigration Minister Alex Hawke revoked his visa for a second time ... now under a "health and good order" rationale. He was scheduled to start playing Monday.

Djokovic left Australia on a plane to Dubai earlier in the day ... but it's unclear where his final destination lies. Serbia's Prime Minister called the decision "scandalous" ... and ND said he was disappointed as well.

One of Djokovic's arguments for being allowed to stay -- even though he's unvaccinated, which is a requirement for anyone traveling down under right now -- was that kicking him out would only fan anti-vaxx sentiments, antithetical to what the Aussie government wants.

The court wasn't buying that though ... and ruled against him. This, of course, comes after Djokovic was cut loose earlier last week when a judge found the government acted too hastily in revoking his visa/detaining him the first time ... but the government struck again under different reasoning the 2nd time -- citing public safety/interest.

Djokovic was given a medical exemption to begin with by two different tennis bodies, because he'd caught COVID in December -- but in the end, the Australian government overrode that ... pointing that, in and of itself, wasn't a loophole that could be allowed on their watch.