The aggressive Marín is now the reigning world and Olympic champion thanks to an imperious 21-19, 21-10 win in Nanjing.
The all-action 25-year-old adds the 2018 crown to her titles in 2014 and 2015, and the Olympic gold she won from the unlucky Sindhu at Rio 2016.
It was more disappointment for Sindhu, who has suffered a string of near-misses in recent times.
There was nothing between the pair coming into the final in Nanjing — in their 12 previous encounters they had won six each.
And so it was in the first game too, as the rivals went toe-to-toe, the more attacking Marín, the seventh seed, bellowing after each winning point.
HISTORY FOR SPAIN!!
HISTORY FOR MARIN!!
HISTORY FOR BADMINTON!!
Carolina Marin: first player to win World Championshops in WS discipline THREE times!
— Badminton Talk (@BadmintonTalk) August 5, 2018
Third seed Sindhu, 23, well known for her never-say-die spirit, initially edged ahead before Marín dragged her back to 16-16.
It was too close to call and the chair umpire had a job on his hands as the two foes repeatedly tried to throw one another off on Marín's serve — the Spaniard wanting to get on with the game quickly but Sindhu refusing to let her in an attempt to kill the momentum.
Sindhu hit into the net to allow Marín to capture the first game in 27 minutes and she took that momentum into the second to make history.
As well as disappointment at Rio 2016, Sindhu was beaten in last year's World Championships final by Japan's Nozomi Okuhara and had to settle for silver at this year's Commonwealth Games too.