Returning from maternity leave after 15 months away, Osaka turned in a fine performance but had no answers for the serve of Garcia as the former US Open semifinalist fired off 13 aces and lost just six points on her first serve.
One break was all the Frenchwoman needed to claim the first set and the second set saw all 12 games won by the server, a tiebreaker going the way of Garcia, who won the last six points to punctuate this first-round blockbuster.
Defeat for Osaka was her first in her career in the opening round in Melbourne as Garcia exacted a measure of revenge after falling to the Japanese star here three years ago.
Garcia dominates on serve to hold off two-time Melbourne champion Osaka
After the server dominated in the opening four games, Osaka, playing in her first major since the 2022 US Open, double-faulted to give Garcia the first break point of the match which she duly converted after the 2019 and 2021 champion sent a forehand into the net for a 3-2 lead.
The Frenchwoman was hunting for a second break and she used her backhand to earn two more break chances but heavy hitting from Osaka and errors off the ground from the 16th seed got her out of trouble.
More long games ensued and Garcia stepped up to the line to serve for the set with a 5-4 advantage and after falling behind 0-30, an ace brought up set point and she converted on her third chance, closing it out with an unreturnable serve.
The second set followed the same pattern as the first set with the server having little trouble holding and each woman looking to dominate from the back of the court. Neither player so much as faced a break point with a tiebreaker deciding things.
Garcia achieved the first minibreak with a clean forehand winner to go in front 3-2 and she would stretch the lead to 5-2 with an ace. Another forehand winner brought up four match points and a backhand into the net by Osaka.