Thiem, a 24-year-old Austrian who was playing in his first Grand Slam final, had 18 unforced errors in first set and 42 for the match.
Nadal now owns 17 Grand Slam championships.
When he was recovering from injury this year, for the umpteenth time in his career, he was focused on this title and nothing - certainly not Dominic Thiem - was going to stand in his way. But after, the Spaniard was imperious. At the following changeover, Nadal was given a salt pill by a doctor and had his left forearm massaged by a trainer.
Nadal's triumph marks the sixth consecutive Grand Slam won by either him or 20-times major champion Roger Federer.
Katherine Lam is a breaking and trending news digital producer for Fox News.
Others - including United States former tennis great Billie Jean King and ex-male professional James Blake - praised Nadal's victory, which was dominant despite an injury scare with hand cramp in the latter stages of the third set. But from 4-all in the opening set, Nadal grabbed five games in a row and was in charge.
Though the sports are so different, Nadal's dominance in the past two weeks - and stretching back to his US Open title in 2017 - bring to mind how sensational LeBron James has been for the Cleveland Cavaliers this season. In those 10 finals, Nadal has dropped just six sets but at no stage in the final on Sunday did it look like the number could rise further. He pounded huge serves, topping 135 miles per hour (220 kph) - about 25 miles per hour (40 kph) more than Nadal's fastest - and that translated into seven aces, but also five double-faults.
After winning 26 of his 27 matches throughout the European claycourt season and 81 of his last 86 sets on clay, there is nothing to suggest Nadal's domination in Paris will end soon.
"I want to say well played to Dominic".
"Rafa, this is one of the most outstanding things an athlete has achieved in any sport", said the seventh seed.
But he could not match Nadal's point-by-point consistency and intensity on Sunday.
Nadal celebrated in relatively low key fashion, but then there is not much novelty value in this. Thiem makes his second double fault in the game.
'Let me enjoy this title', Nadal told reporters.
Still, Nadal was able to complete the job on court Philippe-Chatrier. In the other semi-final, Marco Cecchinato's odd run in the last two weeks was ended by Dominic Thiem, also in straight sets, although the first two sets were somewhat closer than anything Del Potro could muster. At this point, tennis enthusiasts would likely welcome it - but might just as well appreciate Nadal if he were to overpower his way to another Coupe des Mousquetaires piece of hardware.