Is it illegal for a 17-year-old and a 23-year-old to get married without parental consent?

There is no state that will allow someone under the age of 18 to marry without parental consent/court approval/special circumstances. However, once you're 18, you'll be able to get married in any state, with the exception of Mississippi (where you have to be 21) and Nebraska (where you have to be 19).