The Flag of the Canton of Basel in Switzerland is a bicolor flag composed of three equal vertical stripes. The left and right stripes are white, while the central stripe is the canton's coat of arms, featuring a black square on a yellow background with an M for "Mnster" (Monastery) in red. This design represents the historic alliance between the cities of Basel-Stadt and Basel-Landschaft within the Canton of Basel. The flag has been officially used since 1937.