To enter Mexico, a U.S. citizen does not need to show even a passport. All that is required is any valid U.S. ID. However, to re-enter the country, there are requirements that the U.S. government has, which need to be upheld to re-enter the country (see Resources).
Individuals from Andorra, Argentina, Australia, Austria, Belgium, Canada, Chile, Costa Rica, the Czech Republic, Denmark, Finland, France, Germany, Great Britain, Greece, Hungary, Ireland, Island, Israel, Italy, Japan, Liechtenstein, Luxembourg, Monaco, Netherlands, New Zealand, Norway, Poland, Portugal, Puerto Rico, San Marino, Singapore, Slovenia, Spain, South Korea, Sweden, Switzerland, Uruguay and/or Venezuela need not have a passport to gain entrance into Mexico. Instead, citizens from these countries must show a valid passport and have the necessary tourist or business paperwork filled out and presented at Immigration and Customs upon entry into the country. These forms can be obtained at travel agencies, on board planes en route to Mexico, or from Immigration and Customs officials in Mexico.
If an individual is from a country not listed above, then she must go to a Mexican embassy or consulate and request a visa. If she has friends in Mexico, have those friends contact the National Immigration Institute (INM for short) of Mexico. Requirements on paperwork and documentation for getting a visa differ by country.
If you are studying in Mexico, you must be able to prove that you are admitted to and able to financially support yourself in your endeavors as a student in a Mexican university. There are often specific requirements depending on country of origin, so it is important to consult the INM or Mexican consulate.
If you find yourself with a job offer in Mexico, you must prove that you have a job to the INM.
