Daily Mail reports the 32-year-old has been quietly living in Byron Bay to escape the coronavirus pandemic, which has hit the US considerably harder than Australia.
Residents have been reporting sightings of Zac at cafes, however, there has been no photographic proof yet.
One person took to Twitter to share: "My sister just told me that Zac Efron is in Byron Bay."
Last week, influencer Tarsha Whitmore shared a photo of herself in Byron Bay and wrote: "Don’t mean to alarm anyone but Zac Efron was literally eating at the same cafe as me when this was taken."
Zac has not shared his location and has barely posted on social media this year with his most recent post about the Black Lives Matter movement.
He's rumoured to be dating actress Halston Sage, 26, and she has also not disclosed her location, however, she's been posting regularly about work.
One reason why fans believe Zac has been secretly staying in Byron Bay for months comes down to the fact he couldn't take part in the High School Musical reunion in April where the stars reunited via video link.
Zac revealed he was unable to be part of it because of his "bad Wi-Fi" connection fuelling rumours he was living somewhere remote.
In December, Zac was flown to Brisbane after getting sick while filming a TV show in Papua New Guinea.
He took to Instagram to thank his fans for their well wishes, writing: "Very thankful to everyone who has reached out. I did get sick in Papua New Guinea but I bounced back quick and finished an amazing 3 weeks in P.N.G."
On Tuesday morning, shock jock Kyle Sandilands hinted on his KIIS FM radio show that he knew where Zac was staying because he's friends with the actor, but wouldn't share any information out of respect for his privacy.
"I'd rather not say anything... I'm not saying anything," he said.
The radio star continued, "He's a friend of mine and I respect his privacy."
"He's not here for a movie, if he's even here, and he may be... who knows?"
While in Australia in 2017 while promoting Baywatch, Zac appeared on The Project and revealed how much he loves being in Australia.
"I've come out for most of my premieres, every chance I had the opportunity to. [I've] made great friends over the years here. I kind of sneak over here on my own time as well,” he said.
"I've fallen in love with Australia and the fans out here, the people, the culture, the beach. And I do feel like this is kind of my bay, so I really love the idea of maybe shooting the second [Baywatch movie] here."