Saint Piran's Flag (Cornish: Baner Peran) is the flag of Cornwall, England, United Kingdom. The earliest known description of the flag as the Standard of Cornwall was written in 1838. It is used by some Cornish people as a symbol of identity. It is a white cross on a black background.

The flag is attributed to Saint Piran, a 6th-century Cornish abbot. One early use of a white cross and black background design is the 15th-century coat of arms of the Saint-Peran family.

At the Thames Diamond Jubilee Pageant in June 2012, the flag was among those flown on the Royal Barge, Gloriana, though this was explained as "innocent" and "nothing constitutional".

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