Justin Bieber & Orlando Bloom Fight

Miranda Kerr did NOT sleep with Justin Bieber after the 2012 Victoria's Secret fashion show ... so Miranda claimed at the time as did her lawyer.

Miranda's lawyer sent out a letter at the time rumors swirled that Miranda and Justin hooked up at a hotel after the show ... when she was still with Orlando Bloom. The letter calls such claims "false and defamatory."

We're told Kerr was as adamant as her lawyer at the time ... that she did NOT hook up with Bieber.

Apparently Orlando Bloom didn't buy the story. The couple separated the following year. And it's very clear from the story we posted Tuesday night ... there's beef between Justin and Orlando over Miranda.

As for Justin ... sources connected with the singer say he got all braggy when he talked about Miranda ... which of course does not necessarily mean he was telling the truth.

Miranda posted a photo this afternoon on Instagram of herself topless in a bathtub ... just in case you forgot what all the fuss was about.

8:30 AM PT -- We're getting different versions of what incited Orlando, and people are taking sides. One account is Justin extended his hand to Orlando, who refused it, and when Justin asked what's your problem ... Orlando mentioned Miranda. Justin then tried to walk away and that's when Orlando swung.

A second version -- Justin said something to the effect of, I had sex with your wife ... and THEN Orlando swung.

Orlando Bloom threw a punch at Justin Bieber early Wednesday morning in Ibiza ... and Justin fled the restaurant -- this according to 2 eyewitnesses.

The eyewitnesses tell TMZ ... Orlando was in Cipriani restaurant which was packed with celebs, including Paris Hilton, and Diddy.

You don't see Orlando swing, but the eyewitnesses tell us that's exactly what happened. We're told Justin ducked the punch. That's where the video starts and you hear Justin scream, "What's up bitch?"

We're told when Bieber left the crowd applauded.

The backstory is almost legendary ... Justin partied with Orlando's then-wife Miranda Kerr after a 2012 Victoria's Secret fashion show in NYC and they got very VERY close. And in April of this year, Orlando was hanging out with Justin's on-and-off GF Selena Gomez. So the bad blood is flowing.

Hours after the fight ... Justin threw gasoline on the fire by posting -- then quickly deleting -- this pic of Miranda.

Justin Bieber made it clear immediately after he ducked an Orlando Bloom punch -- he was not shaken or rattled.

Justin and a buddy mocked the thwarted punch in the parking lot of Cipriani ... where the altercation went down.

Justin also chatted up some female fans ... knowing of course the photogs were clicking away.

As we reported ... some eyewitnesses claim Justin essentially told Orlando he banged Miranda Kerr... something she has denied.

If Orlando Bloom was worried about Miranda Kerr -- hours before fighting Justin Bieber -- he wasn't showing it because he had his hands full with multiple hot chicks.

Bloom was cruising around the island of Ibiza Tuesday on a speedboat, pumping his fists in the air, dancing with beautiful women ... and looking like he's shouting, "Turn Down for What!" Ultimate bachelor's life.

Looking at these pics, it was VERY GOOD to be Orlando yesterday. Last night? Not so much.

Shoulda stayed on the boat, Orlando.

If Orlando Bloom and Selena Gomez were upset when their wife and boyfriend respectively got all snuggly with each other ... they seem to have had the last laugh.

Orlando and Selena were chilling outside of the Chelsea Handler concert Saturday in L.A. ... but when a photog started snapping pics, Bloom quickly bounced.

It's interesting ... Justin Bieber and Bloom's ex-wife Miranda Kerr got VERY close during and after a 2012 Victoria's Secret Fashion Show ... a number of stories suggested VERY close.

Orlando Bloom and Miranda Kerr are DONE ... the two gorgeous people have announced they're splitting up after 3 years of marriage.

O & M -- who started dating back in 2007 -- released a joint statement through their reps saying, "They have been amicably separated for the past few months. After six years together, they have recently decided to formalize their separation."

"Despite this being the end of their marriage, they love, support and respect each other as both parents of their son and as family."

The couple has one kid together -- their son Flynn, who was born in 2011.

The announcement is pretty shocking considering Miranda and Orlando were spotted out in public together -- smiling and laughing on October 7 in NYC.

And just a couple of months before that, Orlando and Miranda were joking about each other to the media -- with Miranda claiming O has a foot fetish.

We shot Orlando back in July and asked him about it -- and he laughed it off. It's unclear what went south between then and now.

The divorce could get messy when it comes to money -- since they have a ton. According to Forbes, Miranda is the second highest paid model in the world -- raking in more than $7 mil in the past year. And Orlando Bloom's got "Hobbit" money.

It's unclear if the couple has officially filed for divorce at this point -- but it seems like that's just a matter of time.