The flag of Anglesey was registered in March 2014. The design is a banner of the arms ascribed by later mediaeval heralds, to the earlier, locally celebrated ruler, Hwfa ap Cynddelw. The earliest reference to the arms seems to be in the work of the bard Lewis Glyn Cothi from the period of 1447 to 1486 although there is no evident explanation for the choice of colours or charges used. A late C15th century stained glass window with the arms refering to Hwfa are apparently depicted in the east window of Llangadwaladr church on the island.

The flag displayed at the summit of Anglesey, Holyhead Mountain.

According to the heraldic historian Scott-Giles, Anglesey County Council used the Hwfa arms informally

before they were incorporated into the design granted to them officially

. Between 1857 and 1950 the arms were used by Anglesey Constabulary

and were also used by the local fire brigade

. An association between the Hwfa arms and the island county of Anglesey is thus long established as clearly demonstrated by their appearance on the ceiling of the reading room at Bangor University where they appear amidst several emblems representing the counties of Wales.

. See also the Anglesey Facebook page at http://www.facebook.com/AngleseyFlag