A banner can be a flag or another piece of cloth bearing a symbol, logo, slogan or another message. A flag whose design is the same as the shield in a coat of arms (but usually in a square or rectangular shape) is called a banner of arms. Also, a bar-shaped piece of non-cloth advertising material sporting a name, slogan, or other marketing message is also a banner.

Banner-making is an ancient craft. Church banners commonly portray the saint to whom the church is dedicated.

The word derives from Old French baniere (modern French: bannière), from Late Latin bandum, which was borrowed from a Germanic source (compare Gothic: 𐌱𐌰𐌽𐌳𐍅𐌰, romanized: bandwa). Cognates include Italian bandiera, Portuguese bandeira, and Spanish bandera.