The position opened up in the popular Vancouver Island tourist town in November when then-mayor Perry Schmunk announced his resignation.
Schmunk said he quit because the hours of a new job conflicted with his mayoral duties.
Two locals, Osborne, 41, and George Smith, entered the race, but Smith decided to drop out after the deadline, forcing the election to go to the provincial government.
Bill Bennett, minister of community, sport and cultural development, has now acclaimed Osborne as the town's political leader.
Osborne is a biologist by training and a founder of Tofino Botanical Gardens.
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