The flag of Vatican City is a vertical bicolour featuring the colour yellow at the hoist of the flag and the colour white at the fly of the flag. Inside the white section of the flag sits the coat of arms of Vatican City.
The flag of Vatican City was officially adopted on 7 June 1929 following the Lateran Treaty which created the new independent state of the Vatican City out of Italy, to be governed by the Holy See.
The colours yellow and white were used by the Papal States prior to them being absorbed by Italy in 1870 and were used for the new flag of Vatican City. The flag's colours derive from the gold and iron colours of the keys of St Peter, represented by the colours yellow and white on the flag. The flag's coat of arms also includes the keys of St Peter, as well as the Papal Tiara.
The flag's ratio is 1:1.