Australians have until Nov. 7 to mail in a vote on whether they support marriage equality before Parliament votes on the issue.
Hemsworth's fiancee, Miley Cyrus, is a huge advocate for gay rights, with her organization, The Happy Hippie Foundation, helping homeless and LGBT youth.
"My whole life, I didn't understand my own gender and my own sexuality," she said in a 2016 interview with Variety. "I always hated the word 'bisexual,' because that’s even putting me in a box. I don’t ever think about someone being a boy or someone being a girl. Also, my nipple pasties and sh** never felt sexualized to me."
See more in the video below.