Satoshi Nakamoto is the anonymous creator(s) of Bitcoin who published the whitepaper on October 31, 2008 and mined the first Bitcoin block on January 3, 2009. Satoshi mined over 1 million BTC and developed the project in its early years before withdrawing and ultimately disappearing. Ever since, Satoshi has not moved any of this bitcoin.
Satoshi’s disappearance left Bitcoin without a central leader who could dictate the direction of the project, a source of strength in the eyes of most bitcoiners.
The atomic unit of Bitcoin is the satoshi, in honor of Bitcoin’s founder.