What is the hat that is a part of the Mexican national costume called?

Sombrero in English refers to a type of wide-brimmed hat from Mexico, used to shield from the sun. It usually has a high pointed crown, an extra-wide brim (broad enough to cast a shadow over the head, neck and shoulders of the wearer) that's slightly upturned at the edge, and a chin string to hold it in place. In Spanish, sombrero refers to any wide-brimmed hat; in Mexico the hat is called "Sombrero de charro".

Sombreros, like the cowboy hats invented later, were designed in response to the demands of the physical environment. The concept of a broad-brimmed hat worn by a rider on horseback can be seen as far back as the Mongolian horsemen of the 13th century. In hot, sunny climates hats evolved to have wide brims, which provided shade. The exact origin of the Mexican sombrero is unknown, but it is usually accepted that the hat originated with Mestizo cowboys in Central Mexico.