The flag of Saint David (Welsh: Baner Dewi Sant) is normally a yellow cross on a black field, although it has also appeared as a black cross on a yellow field, or with an engrailed cross. It represents the 6th century Saint David (Welsh: Dewi Sant; c. 500 – c. 589), a Welsh bishop of Menevia and the patron saint of Wales.
The Flag of Saint David has been used as a flag representing Wales (as an alternative to the Red Dragon flag), in the same sense that the crosses of Saint George, Saint Andrew, Saint Patrick and Saint Piran are used to represent England, Scotland, Ireland and Cornwall (of which they are, respectively, patron saints). It is similar to the arms of the Diocese of St David's.
The flag can be seen throughout Wales, though not as frequently as the Red Dragon. On St David's Day it often plays a central role in the celebrations.