The Bitcoin whitepaper was published in 2008.
On 31 October 2008, an individual or group using the pseudonym Satoshi Nakamoto posted “Bitcoin: A Peer-to-Peer Electronic Cash System” to a cryptography mailing list. The paper proposed electronic payments that could operate without a central bank or trusted intermediary.
The whitepaper came before the Bitcoin network itself. The bitcoin.org domain was registered in August 2008, while Nakamoto mined Bitcoin’s genesis block on 3 January 2009. The first open-source Bitcoin software release followed on 9 January 2009.
The year 2009 is therefore a frequent wrong answer: it marks Bitcoin’s launch, not the whitepaper’s publication. The paper also did not invent every underlying idea; it combined earlier concepts such as public-key cryptography, proof of work, and peer-to-peer networking into a practical digital-cash design.