5 longest reigning WWE United States Champions 

#3 Dean Ambrose (Jon Moxley) was United States Champion for 351 days

Dean Ambrose (Jon Moxley) in WWE

Former Shield member Dean Ambrose captured the United States Championship in 2013 at the Extreme Rules pay-per-view. He defeated Kofi Kingston to capture the title and went on the most incredible run as United States Champion the modern era has seen.

Ambrose was still a part of The Shield at the time of winning gold. He successfully defended the championship against superstars such as Rob Van Dam, Dolph Ziggler, and Big E.

Still our us champion Dean Ambrose! Believe that & believe in the shield pic.twitter.com/RVyvnFwR2Y

— Michael ⭐⭐ (@MWalker_19) May 3, 2014

The Authority placed Dean Ambrose in a Battle Royal with his United States Championship on the line. Ambrose lasted until the very end, only to be eliminated by Sheamus, ending Ambrose's reign.

Ambrose spoke to Inland Empire Weekly during his reign as United States Champion:

"That's one of those things you don't really realize how cool it is until you hold that belt in your hands for the first time and you hear the crowd. Now for me the biggest part of it is elevating the belt. I don't believe a championship makes a wrestler, rather a wrestler makes a champion." Dean Ambrose said (h/t Wrestlezone)

Five years ago today.! Dean Ambrose won the US Champion.Reigns and Rollins won the tag Titles. 👊👊👊 #RomanReigns #SethRollins #DeanAmbrose #BileveIntheShield pic.twitter.com/euvSdOUC4v

— S.R.D. (@SHIELDSECTION) May 19, 2018