The nuptials follow the arrival of the couple's first child together. Knoxville and Nelson welcomed son Rocko Akira Clapp last December. Knoxville, whose real name is Phillip John Clapp, also has a teenage daughter, Madison, from his marriage to ex Melanie Clapp.
Despite his career of pulling off outrageous stunts, Knoxville and new wife have mostly maintained a low profile, and the actor has said Nelson keeps him calm.
"I'm lucky enough to be with someone, and I am happy," he told Knoxville.com. "I feel very lucky. I'm not out running around all the time. I don't party as much as I used to. I'm not partying constantly and constantly battling myself. I'm with someone, and we are very, very happy."
Knoxville's next move is decidedly more outlandish than making it legal with his ladyfriend. The actor appears in the latest installment of the prank-packed hit series, "Jackass 3-D," which lands in theaters on October 15. Even though he and "Jackass" pals like Steve-O and Bam Margera have been staging elaborate shenanigans for years, Knoxville revealed they still shot tons of footage for the upcoming flick.
"Man, we filmed so much stuff. So much great stuff got left out of the film because we just overshot," Knoxville told MTV News earlier this month. He explained the cutting-room bits will be available on a DVD set to hit shelves by the holiday season. "That'll be in '[Jackass] 3.5,' coming out at Christmas."
Leave well-wishes for the couple below!