Adelaide United midfielder Cavallo, who has represented Australia at Under-20 level, becomes the only known current male top-flight footballer to be out.
Cavallo announced the news ahead of the new A-League season in a lengthy social media post.
The 21-year-old said it was “astonishing to know there are no gay professional footballers who are out and actively playing” and that he wanted to show “others who identify as LGBTQ+ that they are welcome in the football community”.
Cavallo has been praised by players in the Australian women’s national side, with Chelsea’s Sam Kerr tweeting “Good for you” and Arsenal’s Caitlin Foord adding: “Respect, the strength to speak out and own who you are.”
In his post, Cavallo said: “Being a gay closeted footballer, I’ve had to learn to mask my feelings in order to fit the mould of a professional footballer.
“Growing up being gay and playing football were just two worlds that hadn’t crossed paths before.
“In football, you only have a small window to achieve greatness, and coming out publicly may have a negative impact on a career.
Respect, the strength to speak out and own who you are 🙌🏽🏳️🌈
— Caitlin Foord (@CaitlinFoord) October 27, 2021
“As a gay footballer, I know there are other players living in silence.
“I want to help change this, to show that everyone is welcome in the game of football, and deserves the right to be their authentic self.”