Chloë Grace Moretz is voting for Kamala Harris ... saying she's going to protect gay women just like her -- the first time she's come out publicly.

The actress posted a picture of her "I Voted Early" sticker stuck to her leg ... letting people in the caption know she's already voted and voted for Kamala Harris.

CGM says there's so much on the line in this election -- specifically mentioning women's rights over their bodies and legal protection for LGBTQ+ individuals ... important issues to her, she says, 'cause she's a gay woman.

Worth noting ... Chloë's coming out isn't some big surprise -- she's been romantically linked to model Kate Harrison for years, even attending a gay women's march earlier this year. However, this is the first time she's officially come out and said she's gay.

Moretz previously played a gay woman in "The Miseducation of Cameron Post" ... a film all about a conversion therapy camp during the early 1990s.

At the time, Chloë talked about how the movie spoke to her personally ... 'cause she grew up in a very Christian town in Georgia and had two brothers who were gay. She says they "dealt with a lot of self-hate."

Moretz is just one of many Hollywood celebs who are throwing their support behind Harris ... with Cardi B, George Clooney, Bruce Springsteen, Taylor Swift, Billie Eilish and more backing Kamala.