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Sabalenka has won all 11 of her matches in 2023 after battling to a thrilling 4-6 6-3 6-4 victory over the Wimbledon champion.
Dropping the opener against Rybakina was the first time Sabalenka had lost a set this year.
After moving in front, Rybakina seemed on course to back up last year's Major success with a hard-court victory in Melbourne, but No.5 seed Sabalenka regained her composure after a nervy start to win a gripping encounter.
Both players were impacted by the wind in the early stages with the roof open at the Rod Laver Arena, although Rybakina adapted the quicker to break and go 2-1 up as Sabalenka skewed a forehand wide.
Despite the Belarusian levelling at 4-4 with a powerful backhand, Sabalenka's errant serving proved costly as five double faults allowed Rybakina move ahead and serve out to take the lead.
The match sprung to life as Sabalenka's serve clicked into gear. Rybakina saved two set points but had no answer on the third as an emphatic ace ensured a decider would be required.
World No.25 Rybakina was then overpowered by Sabalenka's heavy-hitting forehand and, despite saving three break points prior, the latter snatched a vital opportunity to go 4-3 up and then move a game away from glory.
That break ultimately proved the difference but Sabalenka had to hold her nerve, with Rybakina making her serve it out.
Despite a double fault on her first championship point and then being unable to convert her next two, Sabalenka claimed the title on her fourth match point as her opponent's forehand went long, with the relief and emotion pouring out as she dropped to the ground.
Sabalenka became the 58th different female player in the Open Era to secure a grand slam title after overcoming the 57th Major champion Rybakina, who lifted the Wimbledon trophy in 2022.
In the past two seasons, only Iga Swiatek (24) and Jessica Pegula (18) have won more grand slam main-draw matches than Sabalenka (17) as the 24-year-old tasted her first Major success, having made it as far as the semi-finals in three previous Majors.