The flag of Nova Scotia, created in 1858, is a banner of the coat of arms of Nova Scotia, which were granted to the Scottish colony by Charles I, in 1625.
The flag of the modern Canadian province, a blue saltire on a white field, is a simple figure-ground reversal of the flag of Scotland (a white saltire, Saint Andrew's cross, on a blue field), charged with an inescutcheon bearing the royal arms of Scotland, a gold shield with a red lion rampant surrounded by a royal double tressure (a double border decorated with fleurs de lis). The royal arms do not appear on Scotland's flag - they were added to Nova Scotia's to distinguish the flag from the Naval Ensign of Russia which is also a blue saltire on a white field.
The similarity to the Scottish flag reflects the province's name, which is Latin for "New Scotland". Nova Scotia was one of the few British colonies to be granted its own Coat of Arms, and the flag is the only one of the Canadian provinces dating back to before confederation.
Despite continuous usage of the flag to represent Nova Scotia since 1858, the flag was only recognized by the Provincial government of Nova Scotia as the official provincial flag in May 2013, through the Provincial Flag Act (Bill 82), after an eleven-year old girl researching a project realized that no one had recognized the flag officially in 155 years of usage. 
The flag is ranked #12 in the North American Vexillological Association's survey of North American state and provincial flags. 
See also