The world number seven produced another strong performance to make it four wins out of four in Singapore to reach the final.
Elina Svitolina battled her way into a first WTA Finals title-decider after being pushed all the way by Kiki Bertens in Singapore.
Svitolina is just one victory away from claiming the biggest crown of her career following a hard-fought 7-5 6-7 (5-7) 6-4 win on Saturday.
The Ukrainian said she is on a mission to silence the "haters" this week and has surely already achieved that with four victories out of four.
Bertens, only making her debut in the season-ending tournament because Simona Halep was ruled out with a back injury, caused Svitolina plenty of problems with her aggressive approach, but a mammoth 63 unforced errors cost the eighth seed.
Svitolina was more composed and defended superbly throughout an absorbing contest which took two hours and 38 minutes to settle, sealing a place in the final against Karolina Pliskova or Sloane Stephens.
Sixth seed Svitolina was rewarded for a positive start when she secured the first break, Bertens slapping an inside-out forehand wide to go 3-1 down.
The world number nine hit straight back with vigour, applying the pressure with venomous forehands to get back on serve, but a series of errors from the baseline gifted Svitolina another break - and the opening set.
Bertens threw her racket down in fury following one of those unforced errors, but regained her composure to take a 2-0 lead in the second set following some instructions from her coach Raemon Sluiter.
A resilient Svitolina saved four break points before breaking back to level at 5-5, only for Bertens to edge a tie-break which included seven mini-breaks, a rasping return taking it to a decider.
The Dutchwoman was furious with herself once again when she steered an attempted drop shot into the net to give Svitolina a break, yet responded impressively again to win a Svitolina service game which lasted over 13 minutes.
A couple of poor backhands handed Svitolina another break for a 2-1 lead and the unpredictable Bertens was unable to find a way back, the world number seven saving two break points before finally grinding it out.
"It's the last match of the season and I'm going to give my best and leave everything on the court." - @ElinaSvitolina breaks down her @WTAFinalsSG semifinal win and looks ahead to the final! pic.twitter.com/USHnNbJ4jm— WTA (@WTA) 27 October 2018
Svitolina  bt Bertens  7-5 6-7 (5-7) 6-4
Svitolina – 12/36
Bertens – 41/63
Svitolina – 3/2
BREAK POINTS WON
Svitolina – 5/8
FIRST SERVE PERCENTAGE
Svitolina – 59
Bertens – 60
PERCENTAGE OF POINTS WON ON FIRST/SECOND SERVE
Svitolina – 66/56
Bertens – 69/52
Svitolina – 114
Bertens – 111