Ravindra caned 108 off 101 balls and the evergreen Williamson 102 from 94 as the Black Caps amassed a tournament-record 6-362 at the Gaddafi Stadium, Lahore, after electing to bat on a road of a pitch on Wednesday.
Then Santner led from the front with his beautiful spinning, grabbing the three key wickets in his 3-43 as the Proteas fell short on 9-312, despite a remarkable late show of defiance from David Miller, who reached a 67-ball 100no on the final ball of the match.
It's set up a revenge shot for New Zealand in Sunday's final in the Dubai International Stadium after India, conquerors of Australia on Tuesday, defeated them by 44 runs at the same venue last Sunday.
The New Zealanders, such consistent challengers at the business end of ICC one-day events often only to fall just short, will now hope to replicate this sort of dominant performance in the final as they seek a first major one-day title since lifting the Champions Trophy a quarter-of-a-century ago.
On that occasion in 2000 in Nairobi, the Kiwis won by four wickets - against a Sachin Tendulkar-powered India.
"It's a cool feeling. Now we look forward to Dubai - we've had a go there already against India, and we'll give it a go," said Santner, pondering a return to the venue where India have played all their matches while the Black Caps have been jetting between four venues in Pakistan and the UAE.
"Being there and putting them under pressure at times last time in Dubai was good for our confidence going forward."
Santner got everything right on Wednesday. Choosing to bat after winning the toss, he watched Ravindra and Williamson, even when not quite at his best, put on 164 for the second wicket to provide perfect lift-off.
Ravindra, making his fifth ODI ton -- all in ICC global events -- hit 13 fours and a six, looking every inch the new star of New Zealand batting at 25, while the old master Williamson, nine years his senior, cleared the ropes twice along with 10 boundaries.
Showing a pedigree pooch is happy to learn new tricks, Williamson brought up his 15th ODI ton with a cheeky ramp off Wiaan Mulder, and even when the pair departed, New Zealand racked up 110 from the last 10 overs, with Daryl Mitchell, off 37 balls, and Glenn Phillips, off 27, both clouting quick 49s.
"He keeps doing it," said Santner, of the ever-excellent Williamson. "Kane looked as if might be frustrated at times, but he was able to keep going and get through."
Trying to achieve the highest chase in Trophy annals, captain Temba Bavuma (56) and Rassie van der Dussen (69) looked ready to make a fight of it until Santner got rid of the pair as well as the potential match-winner Klaasen for just three.
Klaasen was caught by a diving Matt Henry, who hurt his shoulder in the process, but Santner felt the pacer would be okay for the final.
New Zealand did get a bit sloppy late on with the match already efffectively won when Miller, running short of partners, went on his late rampage, hitting 10 fours and four sixes and scrambling two off the final ball to get to his consolation three-figure score.
"It's a pretty emphatic win on a stage like this, it's a great feeling," said Ravindra after collecting the player-of-the-match award.
"It's always 'what's next?' But for us, it's important we soak in the moment and celebrate as a team together. Kane's hundred, Santner with the ball, there's been some beautiful performances...
"We'll reflect on today, chill out a wee bit tonight and then we get back to Dubai, we'll switch on."
