An Arizona cop got an unexpected surprise when he pulled over a sleek white Jaguar SUV ... only to discover there was no one behind the wheel.

Check out the clip ... After chasing down a white Jaguar SUV for driving into oncoming traffic and running a red light, an Arizona cop walked up to the car, ready for anything -- except finding he had nabbed a driverless Waymo taxi.

ICYDK, Waymo -- run by Google’s parent company Alphabet Inc. -- is designed to pull over when it detects emergency lights and sirens, but looks like this one seriously "freaked out" -- well, that's according to the dispatch notes.

The shocked cop can be heard calling a company rep, saying, "Yeah, there's a bit of a construction area, and it went into opposing lanes of traffic, which is real bad."

A Waymo support staffer eventually showed up to assist the cop.

Waymo later explained the vehicle "encountered inconsistent construction signage" and ended up in an oncoming lane of traffic after being "blocked from navigating back into the correct lane" for about 30 seconds. That’s when the officer pulled in behind it.

Phoenix officials noted the incident ended without further action ... 'cause, according to dispatch notes, the officer was "unable to issue a citation to the computer."

Luckily, no other cars were involved, and no one got injured. Just a high-tech hiccup and a good story for the cops!