World number two and top seed Sabalenka came into the contest on a 15-match winning streak in Australia but was completely outplayed by the former Wimbledon champion on Pat Rafter Arena.
Rybakina wrapped up the first set in 24 minutes on the back of three breaks of serve as Sabalenka, shaking her head at herself in disbelief, sprayed 12 unforced errors across the Queensland Tennis Centre showcourt.
The Kazakh broke Sabalenka again to start the second set and, although there was more fight from the other side of the net, sealed her sixth career title when the Belarussian crashed another forehand wide.
"I want to congratulate Aryna on a great week and a great season last year and hopefully we will meet again in Melbourne," the Moscow-born world number four said in the on-court presentation ceremony.
"Despite the score, it's always tough to play you. We push each other, which is great, and we improve in this way so I hope that continues."
The pair split their four meetings last year with two wins apiece, although Sabalenka won the match that mattered most to claim her first Grand Slam title at Melbourne Park.
"Honestly, I don't know where to start," said a laughing Sabalenka. "Elena, wow, I don't know where to start. Thank you for those three games, at least we made it look like a fight.
"Couple of words to my team, you did a bad job today. 6-0, 6-3, that's all your fault guys," she joked. Hopefully we'll be better at the Australia Open."
Dimitrov's experience and court craft won out over Rune's youthful athleticism in the men's final, an engrossing contest with plenty of high-quality tennis that kept the crowd gripped for more than two hours.
The Bulgarian, whose game was once often compared to that of Roger Federer, clinched a tight first in the tiebreak but world number eight Rune would not back down.
The Dane, who regularly found aces to get himself out of trouble, fought off a break in a 17-minute game early in the second set and saved three championship points to hold for 4-5.
Dimitrov served out to love, however, claiming the ninth title of his career, and a first since he won the ATP Tour finals in London back in November 2017, with a beautifully judged backhand at the net.
"It's been a while since I held one of these," an emotional Dimitrov said after receiving the trophy for the second time after his 2017 Brisbane triumph.
"I'm fairly tired and I'll take a few days off but I'm really happy to be in Australia. I'll keep on going and yeah, onto the next one."