McIlroy will return to Melbourne in December to chase a second Open crown, eight months after becoming the first player since Tiger Woods to win back-to-back Masters green jackets.
It is part of a two-year commitment from the current world No.2, whose appearance at Royal Melbourne last year set off a surge in international interest.
"There's a huge halo effect that Rory brings," GA chief executive Sutherland said at the 2026 Open launch at host course Kingston Heath on Friday.
"He brought that last year to the tournament locally and with fans and ticket sales and the atmosphere.
"That was coupled with playing at Royal Melbourne and it's the same with playing here at Kingston Heath.
"There's a real afterglow and a delay factor - people not only noticed the event last year but they're talking about it."
Sutherland did not confirm any other high-profile international participants for the 2026 Open, but expects another hot field.
Australian stars Cameron Smith, Adam Scott and Min Woo Lee headlined last year's event with McIlroy.
"We think the demand for players to play is going to be higher than it's ever been," Sutherland said.
McIlroy won the 2013 Open at Royal Sydney and was tied for 14th behind Denmark's Rasmus Neergaard-Petersen last year.
In a video message, the Northern Irishman said he was excited about the prospect of returning to Melbourne in December.
"I always have a great time in Australia," McIlroy said.
"(It has) some of the best golf in the world and I can't wait to get back down there and play in front of everyone."
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