The 23-year-old American teamed up with Aaron Peirsol, Brendan Hansen and Jason Lezak to claim the historic gold in a new world record time.

They held off Australia and Japan to claim glory in a world record time of three minutes 29.34 seconds.

Phelps admitted to being overwhelmed after achieving his feat, and was quick to pay tribute to his team-mates.

"I don't even know what to feel right now," Phelps said.

"There are so many emotions going through my head and so much excitement. I kind of just want to see my mom.

"Without the help of my team-mates this isn't possible.

"I was able to be a part of three relays and we were able to put up a solid team effort and we came together as one unit.

"For the three Olympics I've been a part of, this is by far the closest men's team that we've ever had.

"I didn't know everybody coming into this Olympics, butI feel going out I know every single person very well. The team that we had is the difference."

He added: "Nothing is impossible. With so many people saying it couldn't be done, all it takes is an imagination, and that's something I learned and something that helped me."