World number one Nadal defeated South Africa's world number 32 Kevin Anderson 6-3, 6-3, 6-4 in a brutally one-sided final during which he did not face a break point.
Nadal also claimed an unprecedented 10th French Open in June after finishing runner-up to Roger Federer at the Australian Open.
"In terms of results, this has been one of the best seasons of my career, of course," Nadal admitted of a year in which he won at least two Slams for the fourth time in his career.
Had he gotten the better of Gilles Muller at Wimbledon, where he lost the final set of his fourth-round clash 15-13, the year might have been even more memorable.
"I have been winning titles, playing three finals of Grand Slams, so that's a lot. That's so difficult. The other slam that I was not in the final, I lost the match 15-13 in the fifth to be in the quarterfinals.
"So was very competitive year for me. And on clay, I won almost every match. Of course is an emotional season because I have been through tough moments in terms of injuries."
Nadal's win on Sunday was the latest chapter in an epic story of domination by the sport's superstars.
From Wimbledon in 2003, an incredible 53 of 58 Slams have now been claimed by just five men -- Federer (19), Nadal (16), Novak Djokovic (12) and Andy Murray and Stan Wawrinka with three apiece.
Only Andy Roddick, Gaston Gaudio, Marat Safin, Juan Martin del Potro and Marin Cilic have broken the spell.
"We are are in an era that is not nice to say, because I'm part of it, but we are in an era that some players make incredible things in this sport," said Nadal.
"It's difficult to win a lot of titles. We should be very happy. Probably even Roger and me and Novak, much more than we ever dreamed."
To hammer home their enduring appeal and dominance, Federer and Nadal shared the four Slams in 2017 -- Federer winning the Australian Open before capturing a record eighth Wimbledon.
