Satoshi Nakamoto is the founder of Bitcoin and initial author of the Original Bitcoin client. He has said in a p2p foundation profile that he is from Japan. Beyond that, not much is known about him.
He left some clues about why he is doing this project with the inclusion of the following text in the Genesis block, "The Times 03/Jan/2009 Chancellor on brink of second bailout for banks".
Some more interesting quotes:
Yes, [we will not find a solution to political problems in cryptography,] but we can win a major battle in the arms race and gain a new territory of freedom for several years.
Governments are good at cutting off the heads of a centrally controlled networks like Napster, but pure P2P networks like Gnutella and Tor seem to be holding their own.
It's very attractive to the libertarian viewpoint if we can explain it properly. I'm better with code than with words though.
His identity and/or nationality are in doubt. While the few bits of information available about him point to Japan, he never wrote a single line of Japanese, the Bitcoin client has no Japanese version and there is no Japanese page on bitcoin.org.