Awful news from Tony Hawk — the skate legend says he suffered a broken leg on Monday … and it’s so severe, he may never get back to 100% again.

The 53-year-old opened up about the setback in a lengthy Instagram post on Tuesday … saying he’s going to do whatever it takes to get back on the board again — but it’s not going to be easy.

“Yesterday sucked,” Hawk said. “I broke my elbow 20 years ago and managed to make a full comeback; this recovery for a broken femur will be much harder because of its severity (and my age). But I’m up for the challenge.”

We’re told the injury happened while Tony was skating … but unclear what exactly went down.

Tony says there’s a bit of irony surrounding the accident, as it happened right before the release of HBO’s “Until The Wheels Fall Off” … a doc that details how and why he’s continued to skate into his 50s.

Hawk has previously vowed to keep skating until he literally cannot anymore … and says this injury will be the biggest threat to his ability to continue the sport he loves.

Despite the serious injury, Hawk’s already planning his comeback … and posted incredibly impressive visual proof of that with a pic and video showing him putting weight on the broken leg just one day later!!

Get well soon, Hawk.