James Andrew Byrnes (born May 22, 1983) is a Canadian rower and Olympic gold medallist.

He has won four World Rowing Championships medals: a bronze in 2006 in the men's coxed pair with Derek O'Farrell and Brian Price, and a gold in 2007, a silver in 2009, and a bronze in 2011, all in the men's eight.

He won a gold medal at the 2008 Summer Olympics in the men's eights with Ben Rutledge, Kyle Hamilton, Malcolm Howard, Adam Kreek, Kevin Light, Dominic Sieterle, Jake Wetzel and cox Brian Price.

His teammates included Malcolm Howard and Brian Price, who he won gold with in 2008.

The other six were Gabriel Bergen, Jeremiah Brown, Will Crothers, Douglas Csima, Robert Gibson and Conlin McCabe.