Insane Video of Man Allegedly Stealing, Crashing Yacht into Boats in Newport

Newport Beach Harbor looked more like a bumper boat's course after one man allegedly stole and crashed a multi-million-dollar yacht into other boats ... prompting a police response.

Check out the insane video, you see the man attempt to reverse, and then go forward in full speed -- wrecking into other vessels -- including a sailboat that totally loses its mast in the collision.

Law enforcement sources tell TMZ they got a call just after 10 AM Thursday morning for a "possible stolen vessel."

An eyewitness tells us a police boat eventually arrived on scene and got the boat stopped.

We don't yet know who the alleged thief is, or what his plan was in taking the boat.