Marching band is a physical activity in which a group of instrumental musicians generally perform outdoors and incorporate some type of marching (and possibly onto other movements) with their musical performance. Instrumentation typically includes brass, woodwinds, and percussion instruments. Most marching bands use some kind of uniform (often of a military style) that include the school or organization's name or symbol, shakos, pith helmets, feather plumes, gloves, and sometimes gauntlets, sashes, and/or capes.

Marching bands are generally categorized by function, size, age, and by the style of show they perform. In addition to traditional parade performances, many marching bands also perform field shows at special events like competitions. Increasingly, marching bands are performing indoor concerts that implement many of the songs, traditions, and flair from outside performances.