A lucky driver narrowly avoided being crushed under a massive boulder that rolled down from the roadside hills.

Dash-cam footage shows the moment the giant rock that is about the size of a small car tumbles across a mountain road near Yibin, in south-western China's Sichuan Province, at around 07:40am on August 24.

The video then shows the driver slamming hard against the brakes to avoid getting swept away by the boulder.

The rock knocks down at least two large trees that are in its path before it smashes through the guardrail and continues rolling downhill at speed, vanishing from sight.

Seemingly worried that more might follow, the driver - surnamed Li - puts the car in reverse and drives backwards as far as he can.

Li later told local media he encountered the rockfall near the entrance of a tunnel. Although he had travelled the same road often before, it was the first time he had experienced anything similar.