When you need a calm, soothing voice to get you through a traumatic event, you don’t think of Mike Tyson … but that’s exactly what happened to a motorcycle crash victim.

Ryan Chesley tells TMZ … he was on his way to Las Vegas this week when a cab cut him off on the freeway … sending him flying off his chopper.

Chesley says Tyson saw the whole thing … slammed on his brakes and stopped traffic. Chesley says Tyson — mindful the victim might be in shock — kept him calm until paramedics arrived.

Chesley — who has broken bones, muscles, ligaments, nerve damage and needs shoulder surgery — tells TMZ he’s sending Tyson a thank you note and a fruit basket.

Mike Tyson … he can hurt you bad, and help you good.

These celebrity stories were brought to us by the fine folks at TMZ.