World number two Rybakina, whose Canadian run has her inching closer to No. 1 Aryna Sabalenka in the rankings, kept her title bid alive with another gutsy comeback, having rallied from a set down to beat Naomi Osaka in the quarter-finals.
Meanwhile, former world number one Iga Swiatek turned the tables on Elina Svitolina, outlasting the Ukrainian 6-3, 1-6, 6-3 earlier on Wednesday to reach her first WTA final of the year in Toronto.
Swiatek, seeded seventh, improved to 5-3 against Svitolina, who had narrowed their head-to-head record with two wins over the Polish star this year.
In Thursday's final, Swiatek will play either American fourth seed Coco Gauff or Australian Open champion Elena Rybakina of Kazakhstan, who is seeded two.
In a match delayed more than an hour by rain, Swiatek raced to a 4-0 lead in the op
ening set, in which Svitolina held serve just twice.
The Ukrainian made Swiatek work to serve it out, saving a pair of set points in the final game of the first.
Energised, she raced through the second set before Swiatek rebounded in the third, breaking Svitolina to love for a 5-3 lead before holding serve to secure the win.
"Against Elina it's always tough, so I'm happy that I won this one," said Swiatek, a six-time Grand Slam champion who will be chasing her first title since she won in Seoul almost a year ago.
"Especially that I came back in the third set playing better. So, yeah, that's for sure a big improvement. I'm proud of myself."