Hello
The 22-year-old fourth seed is the first Italian to win the Melbourne Park title.
Bopanna also became only the third Indian to win a men's doubles Grand Slam title.
The Belarusian second seed is the first woman to retain the Melbourne Park title since compatriot Victoria Azarenka in 2013.
Sinner broke for a 3-1 lead in the fourth set and ran away with the match to snap the Serb's 33-match winning run at Melbourne Park and end his quest for a record 25th major.
Sinner's victory snapped Djokovic's winning streak of 33 matches at the Australian Open going back to 2018 and was the world No 1's first loss in 11 Melbourne semifinals.
Bopanna and his Australian partner Matthew Ebden prevailied in a tense semifinal against Tomas Machac and Zhang Zhizhen.
The German stunned second seed Alcaraz 6-1 6-3 6-7(2) 6-4 in the quarterfinals.
The second-seeded Indo-Australian pair will cross swords with unseeded Tomas Machac and Zhizhen Zhang in the semi-finals.
Gauff set up a semifinal clash with Sabalenka in a rematch of last year's US Open final.
The Indo-Australian pair will now meet the sixth-seeded Argentine duo of Maximo Gonzalez and Andres Molteni.