A truck in Los Angeles smashed full-tilt into an ambulance Sunday ... and the emergency vehicle held two patients when the crash happened.

Check out the video obtained by TMZ ... traffic's totally stopped down at this Culver City intersection with the ambulance slowly approaching -- when the silver truck comes streaking out of nowhere.

It runs smack into the ambulance's side, rocking the vehicle a bit ... though it's strong enough to survive the big hit.

The truck on the other hand didn't fare so well ... with the whole front of the car completely smashed in. That'll take awhile to buff out, we gotta say.

Miraculously, the driver in the truck hops out seemingly unharmed ... and makes his way toward the ambulance -- possibly to check on occupants in the other vehicle.

The Culver City Police Department tells TMZ ... the driver of the truck went to the hospital with minor injuries. They also say two patients were in the ambulance when the cars collided and they also had to be treated for minor injuries.

Police closed down the streets to perform a thorough investigation, we're told ... but no arrests were made at the time.