But as he so often does, the Serb found a way.
He captured the decisive break in the third game of the final set, then held firm as Thiem made desperate assaults on his serve.
Going for broke in a nerve-shredding final game, the fifth seeded Austrian went for the lines but missed twice to hand Djokovic one of his most hard-earnt triumphs.
Four months after Nadal stopped Russian Daniil Medvedev in the U.S. Open final, the Serb's 17th Grand Slam title continued the ‘Big Three's' reign over the majors.
Djokovic, Nadal and Roger Federer have now won 13 Grand Slam titles in succession, dating back to Federer's 2017 title at Melbourne Park.
Djokovic has claimed the title every time he has reached the semifinals of the Australian Open, and he maintained that record while closing in on Roger Federer (20) and Rafael Nadal (19) for most majors.
Thiem fell short of a maiden Grand Slam title, losing a third major final but first away from Roland Garros, as the 26-year-old faltered late.
The Austrian missed two forehands to give up a break to Djokovic in the third game of the fifth set before wasting two break points in the fourth.