MATT Ebden has pulled off the biggest win of his grand slam career, upsetting 16th seed John Isner in round one of the Australian Open.

Ebden stunned the American 6-4 3-6 6-3 6-3 to be the first Australian through to the second round at Melbourne Park.

Australia's No.2-ranked men's player behind Nick Kyrgios, Ebden had never previously beaten a top-20 player in a grand slam.

He said after two recent losses to Isner he needed to stay positive. "He is such a great player and so tough to beat so I had to stay composed and find a bit of extra positivity and energy and I think I got that from the crowd, so thank you," Ebden said.

"I am working hard and trying my best and ... it's nice to get some rewards. "I've been playing better the last six to a months, I want to keep it going." The 30-year-old has played some of his best tennis in the twilight of his career, also collecting the scalp of world No.6 Marin Cilic last week at Kooyong.

He has climbed to world No.78 after starting 2017 ranked 699 in the world following a frustrating run with injury.

Edben will next face Ukrainian Alexandr Dolgopolov on Wednesday.