The second seeded Austrian came from behind to beat German fifth seed Alexander Zverev 2-6 4-6 6-4 6-3 7-6(6) to win the US Open on Monday (NZ time).
Thiem became the first Austrian to claim a singles title at Flushing Meadows, albeit in unique circumstances as no fans were present at the hardcourt major due to the Covid-19 pandemic.
The triumph comes after the 27-year-old had come up one short of a major title on three previous occasions.
Thiem was the beaten finalist in this year's Australian Open and at the French Open in 2018 and 2019.