The top-seeded Nadal won the match 6-4, 6-3, 6-2 at Roland Garros in Paris against Thiem, a 24-year-old who is ranked No. 7.
Nadal has won 17 Grand Slam singles titles, three short of Roger Federer, the tennis yin to his yang, who has won a record 20.
Nadal became the first man to beat Federer in a Slam final, ending the Swiss star's hopes of holding all four majors at the same time.
The Spaniard claimed his 11th Roland Garros title with a 6-4 6-3 6-2 victory over Austria's Dominic Thiem on Sunday.
But Nadal roared into the 2017 Australian Open final, losing to Federer, then captured his record 10th French Open crown in June a year ago, setting the stage for another title run in the Flushing Meadows fortnight at the US Open in September.
"I feel very lucky to all of the things that have happened to me".
Halep's coach, Darren Cahill, has said the Romanian enlisted the help of Murray's psychologist, Alexis Castorri, to help land her first major title, per Simon Briggs at the Telegraph.
Thirteen years and 17 Grand Slam titles along, with Nadal aged 32 years and one week, still, nobody has ever said anything any truer.
"I have to come back to speak with my team and decide what's better for my body".
Despite matching Nadal forehand for forehand, Thiem was undone in the 10th game when three errors handed Nadal the opening set after 52 minutes on court.
Nadal avenged his defeat to the Swede at Roland Garros 12 months earlier.
"Difficult for me to think about it now", Nadal said. Fresh from that, the "King of Clay" didn't have enough time to anticipate the follow-up grass court season that was not in his favored manner. What I was really shocked at was that he told us it was cramp in the interview afterwards and then he had treatment for it. I am not much anxious about the future. "You could nearly see the hand start cramping up as the fingers go stiff - it's a frightful feeling", Croft said.
Thiem did at least remind Nadal of his age, saying; "I can still remember being 11 when (Nadal) won here for the first time and I watched on the TV".
Only Nadal, Pete Sampras and Ken Rosewall have managed the feat of winning Grand Slam titles in their teens, 20s and 30s.
But the biggest news from the ATP Rankings was the massive fall of multiple Grand Slam champions Andy Murray and Stan Wawrinka. After guzzling water during that break, Nadal felt better and was back to playing his unmistakable brand of almost unbeatable clay-court tennis.
On Sunday, he even halted play in the third set due to cramping in his finger that affected his blood circulation.