TikTok star Caleb Coffee is lucky to be alive -- but in really rough shape -- after a horrific fall off a cliff in Hawaii and onto lava rock ... sending him to the hospital with serious injuries.

Caleb was hiking with friends Wednesday when he allegedly slipped and fell from a 60-80ft cliff, landing on the rocks below. He was immediately airlifted to a hospital, but has suffered a fractured spine, broken femur, elbow, and wrist with gashes and burns across his entire body.

A GoFundMe created for the 18-year-old features several images of him in the hospital with his family. The page says Caleb didn't have health insurance at the time of his injury, and currently features a goal of $100K in fundraising.

Caleb's got more than 11 million followers on TikTok, and 1 million on Instagram.

His high-energy posts and photos often feature him out in nature, working out and hanging with friends.