A plebiscite postal vote will take place over the coming months to determine whether Australia should follow the likes of the UK, USA and Ireland in legalising same sex marriage.
The issue has caused much divide across the country with many public bodies backing a change and most church groups opposing.
Writing on Twitter on Wednesday, Folau, who represented his country in the 2015 World Cup final, said: "I love and respect all people for who they are and their opinions. But personally, I will not support gay marriage."
I love and respect all people for who they are and their opinions. but personally, I will not support gay marriage.✌❤
— Israel Folau (@IzzyFolau) September 13, 2017
His comments come after the Australian Rugby Union gave its backing to the campaign for change.
Its Twitter logo has the rugby teams badge made up of the pride flag.
Speaking to the Canberra Times, Australia's captain Michael Hooper explained the reasons for why the team was backing a change.
"For a lot of guys, they're about footy and our job is rugby, but sport has ability to cross boundaries," he said.
"We're all very supported of the 'yes' campaign and this is the approach we've taken."
Folau's latest comment has had thousands of 'likes' on the social media site however many have responded with comments of disappointment.