You must be 17 years old, but you must have had a learner's permit for a certain length of time first.
it depends on where your at...im in Illinois and i have to be 16. im pretty sure its that way almost everywhere in the u.s.
sixteen, fifteen and a half for permit.
You can get one at 18, but you won't be able to operate a CMV outside of your home state, nor will you be able to get a hazmat endorsement (not to mention your prospects of being hired as a CMV...
It's the same in any state. 15.5 after complete a driving training course.
16 years depending on what country you are in, I am in Canada.