Man Beaten Senseless in Streets of L.A., Brutal Assault Caught on Video

A brutal assault of a man on the streets of L.A. was caught on camera this week -- and as shocking as the footage is ... what's even more surprising is that no one's been arrested.

TMZ has obtained video that captured this horrific incident early Monday morning -- around 2:00 AM PT, we're told -- where two different parties were facing off on Hollywood Blvd. ... and where one guy who was squaring up (wearing a hat) got pepper sprayed badly.

Unclear what exactly led up to this, but as you can see ... a larger man is hovering on the outskirts of the action, and as the dude in the hat gets riled up, he blasts him in the face.

You can tell it got him directly in the eyes, because he screams out in pain and runs away -- but unfortunately for him ... some other guy who was in the mix took advantage of his weakened state, because he started beating up this blinded man ... mercilessly so too.

Take a look for yourself ... you see this guy in all-black absolutely wailing on the man in the hat -- who's completely buckled under his legs on the ground, and who looks unconscious.

As he continues to strike the defenseless man on the floor, you hear other people yelling at him from the side ... telling him to lay off, noting the guy is down. Eventually, a brave fella comes forward to step in and break it up himself ... throwing something at the attacker.

Even after this ... it looks like the guy in all-black continued to brawl with other people who jumped in ... and at this point, he was freaking shirtless, and STILL throwing punches!

In terms of who used the pepper spray on the victim, again ... no word yet. Law enforcement sources tell us when cops finally showed up for this, there were a few people around who weren't willing to talk. The man on the ground was hospitalized, in bad shape.

Nobody has been taken into custody over this ... and a criminal investigation is underway.