The Flag of the United Kingdom, commonly known as the Union Jack, combines elements from three older national flags. It features the red cross of Saint George, the patron saint of England, the white saltire of Saint Andrew, the patron saint of Scotland, and the red saltire of Saint Patrick, representing Ireland. The design symbolizes the unity of these nations under one flag. The Union Jack is used in various official capacities, including government buildings and military insignia, and is recognized worldwide as a symbol of British heritage and identity.