Machiavelli's title is about as generic as can be, but it still needs some explaining. When the book first circulated in Italy around 1513, it was titled De Principatibus, or About Principalities. In Italian, principato can refer to a whole bunch of political entities, so long as they are governed by a principe. We'll get into that word later. So the focus of this version of the text seems to be a bit different. Remember how the first few chapters are just talking about the different types of places that a leader can rule? Makes sense.
Then, in 1532, Machiavelli's little book was published under a different name, Il Principe or The Prince.
Translations are tricky things. Sure, principe does basically mean prince, but we have a pretty specific idea in our head when we think of princes. Prince Charming, Prince William, basically fairy tales and super old hereditary monarchies and that's it. But principe can mean way more than that. A principe could be a duke, a king, a president, a prime minister, whatever—as long as it's a word that means leader.
We don't know why the title was changed, or if this was the title that Machiavelli wanted all along, but we like it because it's less boring than About Principalities. The title also lets us know the intended audience of the book. Obviously it was specifically meant for Lorenzo de' Medici (who was a duke, by the way), but it speaks to anyone who is thinking about becoming a ruler—even if it's just rule of the chess club.