Novak Djokovic defeated Daniil Medvedev in straight sets to win his fourth US Open and a record-equaling 24th Grand Slam singles title, avenging his loss to the Russian in the final two years ago.

The 36-year-old Djokovic won 6-3, 7-6, 6-3 to become the oldest men's champion in New York in the Open era, which began in 1968, and match Margaret Court's all-time mark for most Grand Slam victories.

"It's hard to describe. I'm really living my childhood dream to compete at the highest level in this sport," Djokovic said. "I never imagined I would be here talking about 24 Slams."

The Serbian is the first man to win three Grand Slam events in the same season four times, crowning his impending return to world number one in the most fitting of ways inside Arthur Ashe Stadium.

The victory added to his wins at the Australian and French Opens earlier this year, with the only blemish his five-set defeat to Carlos Alcaraz in the Wimbledon final, in July.

"First of all I want to ask Novak: What are you still doing here? Come on!" quipped Medvedev, beaten for the fourth time in five Grand Slam finals. "I don't know when you are planning to slow down a little bit."

Medvedev defeated Djokovic in straight sets in the 2021 final to prevent the Serbian from becoming the first man to win all four Grand Slams in the same year since Rod Laver in 1969.

Djokovic admitted to feeling overwhelmed on that occasion, but there was little evidence of nerves as he quickly took command of Sunday's championship match.

Medvedev dethroned last year's champion Alcaraz with a "12 out of 10" performance in the semi-finals, but he struggled to replicate his very best consistently against an imperious Djokovic. (AFP)