Fresnillo /fres'nijo/ (2005 census pop. 110,892), founded in 1554 by Francisco de Ibarra, is the second largest city in Zacatecas state, north central Mexico. As a rail and highway junction, Fresnillo is the center of a rich mining area known especially for silver, and the location of one of the world's richest silver mines, the Mina Proaño or Fresnillo Mine, which belongs to the Peñoles mining company. It has a mining school, and agriculture (cereals, beans) and cattle raising are other important economic activities. Fresnillo is also the municipal seat of the municipality of the same name which surrounds it. The municipality had a population of 196,538 and an areal extent of 4,947 square kilometres (1,910 sq mi).

It is the location of religious pilgrimages to see the famous Santo Niño de Atocha ("Holy Child of Atocha"), a Roman Catholic devotional statue brought to Mexico from Spain.

Between 1551 and 1552, Diego Fernández de Proaño embarked on several explorations in the Zacatecas region, searching for a legendary hill purported to contain great mineral wealth. He discovered a hill, which despite not matching the descriptions given, bore evidence of rich mineral deposits, which he named "Cerro de Proaño" ("Proaño's Hill"). He returned to the city of Zacatecas to report his findings to the Viceroy, but apparently there was not much interest in his discovery and Proaño's Hill was forgotten over the years.