I got my first one when I was 18. I had to get a secured one since I didn't make much money at the time.
I made a blog entry about getting and using a credit card and credit history since a lot of us here are right around the age to get started on that kind of stuff.
https://mlpforums.com/blog/2138/entry-18979-getting-started-credit-card-credit-history-the-easy-way/
So do you have/use credit cards?
How old were you when you first got one?