Authorities said the 34-year-old and an unidentified passenger were in his 2007 Porsche when it careened off the road, flipped over a guardrail and crashed into the woods before bursting into flames.
Both Dunn and his passenger were severely burned. Police said they were able to identify Dunn through his tattoos and hair, but the identity of his passenger was still unknown.
The force of impact shattered the vehicle into several twisted and blackened pieces, leaving the Porsche 911 GT3 unrecognizable. The cause of the accident has not been determined, but police say speed may have been a factor.
A few hours before the 3 a.m. crash, Dunn tweeted a picture of himself drinking with two friends, but the photo has since been removed.
Dunn appeared on MTV shows "Jackass" and "Viva La Bam" and the three "Jackass" big-screen adaptations.
"We are devastated by the tragic loss of Ryan Dunn - a beloved member of the MTV family for more than a decade," said Van Toffler, president of MTV Networks Music/Films Group. "The Jackass brotherhood will never be the same."
His longtime friend and fellow "Jackass" daredevil Johnny Knoxville tweeted on Monday afternoon, "Today I lost my brother Ryan Dunn. My heart goes out to his family and his beloved Angie. RIP Ryan, I love you buddy."
Dunn's most famous skits included diving into a sewage tank and shoving a toy car into his rectum.
He also was the star of his own MTV show, "Homewrecker," and hosted "Proving Ground" on the G4 cable network.
The Associated Press contributed to this report.