Nenshi, who has been elected twice as mayor, is just one of four North American mayors, and 26 mayors worldwide, to be nominated for the prize.
The honour, first awarded in 2004, is awarded every two years by the City Mayors Foundation.
"The City Mayors Foundation and the World Mayor Project were established in 2003 to promote, encourage and facilitate good local government," the foundation's website reads.
Iñaki Azkuna, Mayor of Bilbao, Spain, won the award in 2012.
Voting closes on Friday, and the winner will be announced in January.
Of course, we think Nenshi deserves the prize, but we're probably a bit biased. Click through the slideshow to see Nenshi's short list competitors: