The Yukon River Quest claims the title as the worlds longest canoe race.  This event is essentially paddled non-stop (there are two required rest breaks) in a variety of canoe, including BIG Canoes, kayaks and SUP classes.  The race is some 715 km and is paddled from Whitehorse to Dawson City in the Yukon, on the Yukon River.  More details are available on the

Yukon River Quest website