If you are a US citizen traveling to Mexico by air, you will need a valid **US passport book**. However, when traveling via land, a passport book is not a mandatory requirement.
Minors (babies and children) will also need a passport to enter Mexico.
For travel to some countries, a passport needs to be valid for at least six months beyond the date of travel. This is not the case for travel to Mexico, and as long as your passport is valid for the entire period of your trip, you shouldn't have any problems.
