Billie Eilish Smooching BF Jesse Rutherford ... Screw It, Let's Go Public!!!

Billie Eilish and Jesse Rutherford aren't hiding it anymore, locking lips in public and letting the world know they're together.

The two were showed off some PDA Tuesday night in Studio City -- where they were on the streets and making out in front of cameras, no longer blurring lines -- they're a couple and definitely happy.

Check out the photos for yourself ... you can see BE and JR embracing, kissing, holding hands and smiling from ear to ear as they stroll down the street without a care in the world.

It's the third outing we've seen in less than a week where they seemed to be getting cozy. Remember, it all started with a video that surfaced showing them at Halloween Horror Nights looking like a couple. Ditto for a dinner date night the day before.

There's been evidence they've been hanging out since at least August of this year -- when they were photographed at the same movie premiere.

Of course, there's been controversy with this relationship ... mostly among her fans. We're talking about their age difference -- 11 years, more or less -- and the fact that Jesse appears to have known/befriended her when she was underage ... at around 15 or 16 years old.

Some are calling it icky, but Billie and Jesse themselves clearly don't give a rip -- and appear to almost be sticking it to the haters with the over-the-top affection here.

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