Western Storm will face Southern Vipers in a repeat of last year's Kia Super League final after they overcame a top-order collapse to beat Surrey Stars by three wickets in the semi-final at Hove.
After restricting Surrey to 100-7, Storm lost four top-order wickets for five runs in 10 balls as their run chase got off to a terrible start.
But from the wreckage of 17-4 in the fourth over, they were led to victory by West Indies' all-rounder Stafanie Taylor, who made an unbeaten 37 to steer her side home with seven balls to spare.
Surrey's hopes had been raised by a superb spell from South African Marizanne Kapp, who took three wickets in four balls. Her off-cutter deceived England captain Heather Knight (1) and Fran Wilson was lbw to an inswinger off the next delivery. In her next over Kapp had Sophie Luff (5) brilliantly caught behind by Tammy Beaumont diving to her right while Rachel Priest (11) was bowled when Nat Sciver got one to nip back through her defences.
But Taylor and Georgia Hennessy settled Storm's nerves with a stand of 44 for the fifth wicket. Hennessy (21) was bowled by Laura Marsh in the 13th over and Storm were struggling on 67-6 in the 15th over when Lissy MacLeod (2) drove to extra cover.
But Anya Shrubsole hit Alex Hartley for a straight six to get them back on track and although Shrubsole holed out to deep mid-wicket, Taylor adroitly kept finding the gaps. She only hit two fours but her 37 off 46 deliveries made the difference.
Earlier, Surrey had struggled to get any momentum after winning the toss. The pitch lacked pace and only Sophia Dunkley, who scored 30 from 33 balls, got to grips with the conditions and an accurate attack.
England opener Tammy Beaumont needed 17 deliveries to score three runs and later dropped Hennessy before she had scored while South African Lizelle Lee (10) and England all-rounder Sciver (10) failed to build on promising starts.
Shrubsole picked up three wickets in the last over to finish with 3-22 and was well backed up by Storm's spinners with Claire Nicholas, who took the new ball, the pick with 1-14.
Storm captain Heather Knight reflected: "There was a little bit more in the pitch than we expected but it was still a good wicket and it's great to get over the line.
"Marizanne Kapp bowled a brilliant spell at the start and being 17-4 was not ideal. We just needed someone to stay there. Stefanie (Taylor) has been a bit disappointed with her scores in the tournament so far so it was great for her to come good in the semi-final. She is at her best when she can set the tempo in a run chase and she paced it really well.
Last year we won the semi but then we were a little bit lethargic going into the final so it's important that we make the best use of the time before we play the Vipers."
Surrey Stars captain Nat Sciver couldn't hide her disappointment after the defeat, saying: "Marizanne Kapp got us back in the game with a brilliant spell and we kept at it in the field, but we just didn't get enough runs on the board. If we'd got another 20 runs or so it would have been very interesting, but credit to Stefanie (Taylor) who played a great innings under pressure.
"It's a shame we haven't got through but we have definitely improved as a squad this year and I think the tournament has gone from strength to strength."
Watch Southern Vipers take on Western Storm in the 2017 Kia Women's Super League Final, live on Sky Sports Cricket.