Nadal roared out in the first set, breaking Monfils in the second and sixth games and keeping the Frenchman off the net with deep, well-placed returns that sealed it up in just 25 minutes at 6-1.
Monfils took back some of the momentum early in the second set, delivering strong serves and crosscourt returns — and pleasing the crowd with acrobatic saves.
But the left-handed Spaniard fought back in the 11th game, breaking Monfils’ serve with a long return shot just out of reach that put him ahead 6-5. He then held his serve to take the next game and the match at 7-5.
“I have to enjoy this moment,” the 24-year-old Nadal said, promising to return next year. “You never know when it will end.”
Nadal, who has won nine career Grand Slam titles and seven of eight finals this season, went into the match a heavy favorite, having beaten Monfils in six of their last seven meetings. His only loss to the Frenchman came on Doha’s hard surface last year.
Monfils has also struggled against left-handed opponents, with an 0-3 record against them this season.
“I wanted to win another big title after the US Open,” Nadal said. “Every tournament is very important.”
But Nadal, fresh off an upset loss in Bangkok to compatriot Guillermo Garcia-Lopez, said going into the match that he was tired from a long season and was having trouble concentrating.
Though he breezed through his early matches in Tokyo, winning in straight sets, that fatigue showed in his semifinal against unseeded Viktor Troicki, who was at match point twice and forced the top-seeded Nadal into two tiebreakers before he finally capitalized on the Serb’s sloppy play.
Nadal had only one ace, to nine served up by Monfils, but won 90 percent of points on first serves.
Still, he said he was able to shake off the previous day’s doldrums and was satisfied with his performance Sunday.
“Though there was a lot of tension against Troicki, it wasn’t physically very demanding,” he said, adding that he pushed Monfils hard and saw the win as the product of his own aggressive play rather than Monfils’ early mistakes.
“I started playing at high intensity, and that’s why I won the match,” he said. “I was very comfortable with myself.”
Monfils, who is ranked 15th in the world and defeated second-seeded Andy Roddick in a hard-fought match en route to the finals, said he started off slowly because he warmed up with the arena roof closed and could not get used to the sunlight as it opened just before the competition began.
“It was hard for me to adjust my game,” he said. “It is hard to beat Rafael outdoors.”
Rain pushes back both finals to Monday
In Beijing, the singles finals at the China Open will be completed on Monday after heavy rain halted play in a smoggy Olympic tennis center on Sunday, with champion Novak Djokovic leading Spain's David Ferrer 3-1 in the men's showdown.
New world No. 1 Caroline Wozniacki did not even make it to court and will have to wait another 24 before she can face Russian second seed Vera Zvonareva in the women's showpiece.
Djokovic and Ferrer stepped on court four and half hours later than scheduled after the dense smog that has blighted this week's tournament gave way to a heavy downpour.
When the rain finally relented, stewards hastily wiped down the hard court before the players were called on to Lotus Center Court.
Less than 20 minutes later, Djokovic and Ferrer were hastily packing their bags and running back into the locker room after the heavens opened again, wiping out the rest of the day's play.
The latest weather setback comes after players complained about the smoggy conditions in the Chinese capital, leading Djokovic to suggest earlier in the week that players should have access to oxygen tanks on court to help them breathe.
Unfortunately for Djokovic, the rain failed to disperse the toxic haze that has described as "hazardous" by air quality monitors for five days running.
Tournament organizers have played down health concerns posed by the smog which has also affected UN climate talks taking place in the neighboring city of Tianjin 65 miles away.
