Oleksiak, the youngest and 74th recipient of the award, burst onto the scene in Rio where she became the first Canadian to win four medals at a Summer Games, including gold in the marquee 100 metres freestyle.
She also took a silver in the 100m butterfly and bronze from two relays.
Oleksiak beat out a strong field for the prestigious award that included hockey player Sidney Crosby, sprinter Andre De Grasse and golf's Brooke Henderson.
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The Lou Marsh Trophy, named after a former Toronto Star sports editor, is voted on by a panel of Canadian journalists.
Past winners include Hockey Hall of Famer Wayne Gretzky, Masters champion Mike Weir, Formula 1 champion Jacques Villeneuve, NBA most valuable player Steve Nash and drug-tainted sprinter Ben Johnson.
(Reporting by Steve Keating in Toronto; Editing by Frank Pingue)
