The flag of Sweden dates back to the 16th century. It is believed to be inspired by the Coats of Arms of Sweden, which feature three yellow crowns on a blue background, and modelled on the Danish flag, the Dannebrog. King John III took the form of the current Swedish flag into use in 1569. Prior to this, a similar flag appeared in the Coat of Arms of John's duchy, which is today southwest Finland.

• According to Swedish law 1982:269, the dimensions of the flag are 10/16 (height/width), the inner blue fields having 4/5 and the outer blue fields 4/9 (height/width).
• According to Swedish law 1983:826, the colours used are established through the NCS color system to be: Yellow - NCS 0580-Y10R, blue - NCS 4055-R95B.

See also: Flag days in Sweden, Holidays in Sweden, National anthem of Sweden