Rybakina, 27, dropped only four points in a near flawless performance on serve against four-time Grand Slam champion Osaka.
She faced the 28-year-old full of confidence, having not dropped a set in her opening three matches at the tournament, and took control of the contest in a dominant first set.
Reigning Australian Open champion Rybakina opened up a double break over Osaka, before sealing the set in just 21 minutes.
Osaka showed greater resistance early in the second set but, after failing to convert her only break point of the match, Rybakina soon seized control again.
She broke to go 4-3 up, before safely seeing out the rest of the match, with Osaka unable to contend with her opponent’s deep groundstrokes.
Rybakina sealed the match inside 66 minutes with her seventh ace of a match where she hit a total of 29 winners to Osaka’s nine.