St Georges Flag—the flag of England—flying over lush green English countryside

The red cross on white was first associated with St George, a Christian martyr, and became a common symbol in medieval Europe. In the late 13th century England adopted the St George’s Cross as a national emblem, replacing earlier symbols like the White Dragon and Golden Cross, and later adopted St George as Patron Saint. England’s St George’s Cross is among the oldest, but not the oldest, national flag in use today. England itself became a unified kingdom in 927 AD under King Æthelstan, making it one of the earliest continuously existing nation-states in the world, with borders that have barely changed.