The Lions recovered from being 3-22 down on 38 minutes to beat the Hurricanes 44-29 and secure a home final against the Crusaders.
It was the fightback of all fightbacks from the South African side as tries from Jacques van Rooyan, Ross Cronje, Malcolm Marx, Harold Vorster, Elton Jantjies and Kwagga Smith saw them dominate the second-half in Johannesburg.
For the 'Canes they were shocked after the interval as TJ Perenara, Wes Goosen, Ardie Savea and Ngani Laumape's tries came in defeat.
The Hurricanes had blown away their hosts in the first period with a brand of rugby that had the Lions struggling to deal with their opponents.
Chris Boyd's men crossed three times - through Perenara, Goosen and Savea - but thanks to a try from Van Rooyan, the Lions stayed in touch.
Jantjies opened the scoring on five minutes with a penalty after side entry from the 'Canes but he would soon make a mistake, with a loose offload seeing Perenara collect, kick ahead and regather for the game's opening try. Jordie Barrett was wide with the conversion attempt.
They weren't finished and when a set move off a line-out saw Beauden Barrett slice through a gap and find Goosen for a score, it was 12-3.
It was relentless from the visitors as their handling skills and ability to keep the ball alive was hurting the Lions who looked out of sorts.
Jordie Barrett turned the screw on 20 minutes with a penalty and then also went close to scoring on the right wing but for good scrambling.
Things got worse for the Lions on 30 minutes when Savea raced over after collecting Cronje's fumble and suddenly it was 22-3 to the 'Canes.
Fortunately for the Lions they did get over the line before the break thanks to Van Rooyan's powerful carry, which kept their hopes alive.
The second-half was drastically different to the first as it was all the Lions thanks to a score five minutes in from Cronje a metre out.
It was clear the home fans sensed the shift in momentum and their players duly responded to the encouragement with a line-out drive seeing Marx go over. The missed conversion from Jantjies meant it was 22 apiece on the scoreboard with just 14 minutes gone in the second period.
The Hurricanes needed to dig in and they did more than that when Laumape finished off on the right following slick hands in the backline.
However, the 'Canes smiles were shortlived as after Beauden Barrett was yellow carded, three points from Jantjies and a score from Vorster after a nice line short to the ruck pushed the Lions 32-29 up. It was looking more and more likely that the final would be in Johannesburg.
And that was rubber stamped on 70 and 75 minutes as, from five metres out, first Jantjies went through a hole before adding the extras for 39-29 and then replacement Akker van der Merwe set up Smith for a run-in, sparking celebrations at Ellis Park as the Lions make back-to-back finals.
Tries: Van Rooyan, Cronje, Marx, Vorster, Jantjies, Smith
Cons: Jantjies 4
Pens: Jantjies 2
Tries: Perenara, Goosen, A Savea, Laumape
Cons: J Barrett 2, B Barrett
Pen: J Barrett
Yellow Card: B Barrett
Lions: 15 Andries Coetzee, 14 Ruan Combrinck, 13 Lionel Mapoe, 12 Harold Vorster, 11 Courtnall Skosan, 10 Elton Jantjies, 9 Ross Cronje, 8 Ruan Ackermann, 7 Kwagga Smith, 6 Jaco Kriel (c), 5 Franco Mostert, 4 Andries Ferreira, 3 Ruan Dreyer, 2 Malcolm Marx, 1 Jacques van Rooyen
Replacements: 16 Akker vd Merwe, 17 Corne Fourie, 18 Johannes Jonker, 19 Lourens Erasmus, 20 Cyle Brink, 21 Faf de Klerk, 22 Rohan Janse van Rensburg, 23 Sylvian Mahuza
Hurricanes: 15 Jordie Barrett, 14 Nehe Milner-Skudder, 13 Vince Aso, 12 Ngani Laumape, 11 Wes Goosen, 10 Beauden Barrett, 9 TJ Perenara, 8 Brad Shields, 7 Ardie Savea, 6 Vaea Fifita, 5 Sam Lousi, 4 Mark Abbott, 3 Jeff To'omaga-Allen, 2 Dane Coles (c), 1 Ben May
Replacements: 16 Ricky Riccitelli, 17 Chris Eves, 18 Loni Uhila, 19 Reed Prinsep, 20 Callum Gibbins, 21 Te Toiroa Tahuriorangi, 22 Otere Black, 23 Julian Savea
Referee: Jaco Peyper
Assistant Referees: Marius van der Westhuizen, Rasta Rasivhenge
TMO: Marius Jonker