James Magnussen, born April 11, 1991, Port Macquarie, New South Wales, Australia, is an Australian swimmer. He is the current 100-meters freestyle world champion (as of 2012).

During the 2011 World Aquatics Championships, Magnussen was the starter for the Australian relay team in the 4×100 metre freestyle relay. His time of 47.49 eclipsed Pieter van den Hoogenband’s (pre-polyurethane suit) former world record, and is the fastest swim ever over that distance by a swimmer not wearing the now-banned suit.

At the 2012 South Australian Championships, Magnussen clocked a 48.05 to climb to the top of the early world rankings in the 100m freestyle. The next day he set a new personal best time in the 50m with a 22.41.

At the 2012 Australian Championships he clocked 47.10 to win the 100m Freestyle, with the victory he became the 4th fastest swimmer in the history of that event. He also won the 50m Freestyle in 21.74, the fastest any Australian has ever been in textile swimwear in that event and the first person to crack the top 25 since the ban of the suits.