Top seed Nadal claimed a dominant victory over Thiem, despite suffering an injury scare when he suffered cramp in his left hand when 3-1 up in the third set.
Nadal’s win extends his record of titles at the French Open to 11, and means he has won 17 Grand Slams in total, just three behind Swiss great Roger Federer.
Nadal, 32, returned to action following a three-month layoff, after a hip injury forced him to retire from the Australian Open in January.
It never gets old, does it @RafaelNadal?
The King of Clay captures his 11th Roland-Garros title 6-4 6-3 6-2.
Rien n'arrête Rafa ! 11e titre pour l'Espagnol ici à Roland-Garros et son 57e titre sur terre-battue.
— Roland-Garros (@rolandgarros) June 10, 2018
However, the King of Clay has been in fine form in Paris, and has dropped just one set on his way to a record-extending 11th title.
Thiem, 24, is touted as a potential Grand Slam winner of the future, but was no match for Nadal on his favored surface, with the Spaniard powering to victory in around two and half hours.
Nadal has won each of the finals he has contested at Roland Garros, and has won 11 of the last 14 French Open titles.