The Union Flag, commonly known as the Union Jack, is the national flag of the United Kingdom. It combines elements from three older national flags: the red cross of Saint George for England, the white saltire of Saint Andrew for Scotland, and the red saltire of Saint Patrick for Ireland. The flag symbolizes the unity of these nations under one sovereign. The design of the Union Flag was officially adopted in 1801. It is used in various official capacities, including government buildings and military uniforms. The flag is also a popular symbol of British identity and is often displayed during national celebrations and events.