The legal age for renting a car varies from country to country. In the US it is generally 18 years old, for certain types of vehicles (utility vans and luxury cars) you need to be at least 25 years old. Only New York and Michigan have state laws requiring car rental agencies to rent to drivers age 18 and over, all other states allow companies to set their own age requirement at their discretion.  Most agencies in Europe allow rentals from the age of 21. Certain brands such as Sixt or Europcar accept it from the age of 18, under certain conditions (years of driving experience, vehicle category).  Note that agencies almost always apply additional fees if you are a young driver.