Mexican string orchestra composed of 3 to 12 performers playing a variety of stringed and brass instruments. (In addition to referring to an ensemble, the term mariachi is also used for the individual performer of mariachi music or for the music itself.) Mariachi has long been considered a uniquely Mexican sound, representing a homegrown tradition that embraces both indigenous and foreign elements.

The mariachi orchestra emerged in the late 1700s or early 1800s in west-central Mexico. The word itself may have come from the now-extinct language of the Coca Indians, but both the word's etymology and the early history of the form and its followers are unknown. The typical instruments of contemporary mariachi include the vihuela, a type of guitar having six double courses of strings, popular in the Spanish Renaissance; the guitarrón, a large, fretless six-string bass guitar; and a standard five-string guitar. Violins and trumpets, which usually play the melody, are later additions, and they are now more or less essential elements. Mariachi music initially consisted of local or regional sones (instrumental music), but, early on, performances began to include vocal elements.

Early mariachis dressed in peasant garb (usually white), though since the early 1900s male mariachi bands typically have worn traje de charro, the attire of the cowboys of Jalisco—matching uniforms with tight, ornamented trousers, boots, wide bow ties, sombreros, and short jackets. The traditional ensemble was all-male, but since the 1940s women have played an increasing role in mariachi performance—to the degree that the by the late 1990s there were a number of all-female mariachi groups.