Rybakina, 25, became the first man or woman from Kazakhstan to win a grand slam when she lifted the Wimbledon trophy in 2022, and she is now two matches away from securing her second.
Against Latvia's Ostapenko, Rybakina had a clear power advantage, illustrated by her 11 aces while conceding only one.
She secured a break in the first game of the match, and quickly grabbed a second to race through the first set in 33 minutes.
It was Ostapenko who snagged the early break in the second set, but she was unable to consolidate it, failing to hold serve in each of her next two chances to allow Rybakina to claw back in front.
Ostapenko will rue some wasteful play as she finished with more break point opportunities than her victorious opponent, but was only able to convert one of her eight chances.
Rybakina will meet the winner between Jessica Pegula and Victoria Azarenka in the semi-final.