Nobody knows, and even if someone does — they are keeping quiet about it. The fact is that Satoshi is the only one who can prove his/her/their identity, and he/she/they decided not to do so. Satoshi might be a single person, a group or a team, or even a company or an agency. It is a great topic if you like conspiracy theories, and it gets wilder and wilder as you get deeper into it. In the end, however, it doesn't matter who Satoshi is, and most people actually like a bit of mystery regarding Bitcoin's creator.