Events in the year 1842 in Mexico.

• President:
  • Antonio López de Santa Anna until October 26
  • Nicolás Bravo after October 26

• Aguascalientes:
• Chiapas: Salvador Ayanegui
• Chihuahua:
• Coahuila: José Ignacio de Arizpe/Francisco Mejía
• Durango:
• Guanajuato:
• Guerrero:
• Jalisco: Antonio Escobedo
• State of Mexico:
• Michoacán:
• Nuevo León: Manuel María de Llano
• Oaxaca:
• Puebla:
• Querétaro: Sabás Antonio Domínguez/José Francisco Figueroa/Julián Juvera
• San Luis Potosí:
• Sinaloa:
• Sonora:
• Tabasco:
• Tamaulipas: Jose Antonio Quintero
• Veracruz:
• Yucatán: Miguel Barbachano
• Zacatecas:

• March 5 – Mexican troops led by Rafael Vasquez invade Texas, briefly occupy San Antonio, and then head back to the Rio Grande. This is the first such invasion since the Texas Revolution.

• September 8 – Juan José Carrillo, Mayor of Santa Monica, California was born in Santa Barbara, Alta California (died 1916)
• October 8 – Francisco del Paso y Troncoso, historian and Nahuatl scholar was born in Veracruz, Veracruz (died 1916)

• August 24 – Leona Vicario, supporter of the Mexican War of Independence and wife of Andrés Quintana Roo (born 1789)

• Silvestre De León, soldier and third Alcalde of Victoria murdered in Victoria (born 1802)^[1]
• José Mariano Elízaga, composer died in Morelia (born 1786)
• Agustín V. Zamorano, printer and Governor of Alta California died in San Diego (born 1798)