After their colleagues had departed following breezy fifties on a good M Chinnaswamy Stadium track on Sunday, Iyer (128 not out) struck his fourth ODI ton before Rahul (102) exploded as the duo lit up the stage on the Hindu festival of Diwali to get India to 4-410.
Requiring a record World Cup chase to win, the bottom-placed Dutch side got good starts from Max O'Dowd (30), Colin Ackermann (35), Sybrand Engelbrecht (45) and Teja Nidamanuru (54) but never threatened and were dismissed for 250 in 47.5 overs.
Mohammed Siraj (2-29) overcame a throat injury, suffered when he dropped a catch, and ended up dazzling alongside Kuldeep Yadav (2-41), Jasprit Bumrah (2-33) and Ravindra Jadeja (2-49) to secure victory for India, who face New Zealand in the semis on Wednesday in Mumbai.
Iyer reached his century in 84 balls and finished with 10 fours and five sixes while Rahul needed only 62 balls for his ton, getting there with two huge sixes in the last over that took India past 400.
The duo forged a 208-run partnership - the highest fourth-wicket stand in World Cups - as India scored 126 runs in their final 10 overs to post the third total above 400 in the event.
KL Rahul (l) and Shreyas Iyer (r) were twin centurions in India's win over the Netherlands.
"Shreyas is the backbone of our middle order and we all know how tough it's been for us to find a good number four batter for the last 10 years," India coach Rahul Dravid said on Star Sports.
India put the Netherlands to the sword after winning the toss and opting to bat as skipper Rohit Sharma (61) and Shubman Gill (51) smashed boundaries at will to give them a superb platform with 91 in the powerplay.
Gill was severe on the bowlers with three fours and four sixes, but the world's top-ranked batsman found the fielder in the deep while taking on a short one from Paul van Meekeren after reaching his 12th half-century.
The Netherlands chipped away and were rewarded when Bas de Leede had Rohit caught at wide long-on, but Kohli (51) and Iyer took India past 200 runs in the 29th over with a 71-run stand.
Kohli delighted the crowd with a wide array of shots after a shaky start to his quest to reach 50 ODI tons and eclipse Sachin Tendulkar's record, but Roelof van der Merwe briefly silenced fans by breaking his stumps with a flatter one.
"India are a well-balanced side. They have match-winners all the way through. They've shown it in this World Cup," said allrounder van der Merwe.
"They're going to be a tough team to beat. The other teams also, South Africa have got match-winners and the consistency of New Zealand and Australia ... It's going to be interesting, but I think India do shape up well."
