That's the discretion of the rental agency and their insurance carrier. You'll have to have a fully unrestricted license (no restricted or graduated licenses), which means you'll have to be at least 18. Looking on the website for Hertz, their minimum age is 21. On Budget's website, it seems possible that in some states, their policies can vary by municipality, so I looked up the places in Colorado relevant to me - Denver, Broomfield, and Colorado Springs, and the site says for all of them, ""An individual 21-24 years of age may only rent an economy, compact, intermediate, standard, full-size or premium car or an intermediate or standard SUV.", and so I skimmed through other locations, and it appears that's the policy statewide.
In short, it's going to be 21, unless, by chance, you find some small time agency willing to rent a car to an 18 - 20 year-old, although I wouldn't recommend holding your breath waiting to find one.
To rent a car as a 21-year-old, you typically need to be at least 21 years old.
In San Francisco, you must be at least 21 years old to rent a car.
you must be 25 to rent a car out of any major airport in MA.
You must be 25 to rent or drive a rental car.
In Arizona, you must be at least 21 years old to rent a car.
Usually to rent a car you have to be 25 years old. Usually you are required to have a credit card as well.
old enough
25 years old
bazilion
21
sixty
No, most car rental companies require renters to be at least 18 years old, and in some cases 21 years old, to rent a car.