Justin Theroux: New Year's Eve ATV Riding!

Justin Theroux shows off his toned arms while having some fun with an ATV on New Year’s Eve (December 31) in Baja, Mexico.

Earlier in the day, the 41-year-old actor was seen wrapping his arms around his fiancee Jennifer Aniston in Cabo.

PHOTOS: Check out the latest pics of Justin Theroux

Over the weekend, Justin and Jennifer were seen relaxing by the pool while their friends Jimmy Kimmel, his fiancee Molly McNearney, and John Krasinski enjoyed some paddle-boarding together.

10+ pictures inside of Justin Theroux going on an ATV ride…