Campbell edged a close final against Irish challenger John Joe Nevin 14-11 to join Nicola Adams as a British winner in the ring at London 2012.
He told BBC Sport: "I'm lost for words, very emotional. It's something I've worked for all my life. I can't believe it. Nevin's a top fighter, it was a very difficult fight, very technical. It was just about outwitting each other.
"I had to be on my game to win and thankfully I was. I can't believe it. I'm very proud to be from Hull and I really appreciate all the support both there and here in London, thank you."