Bitcoin’s first block is called the Genesis Block.
Satoshi Nakamoto mined this block on 3 January 2009, creating the starting point of Bitcoin’s blockchain. It is also known as block 0, although some Bitcoin software treats it differently from later blocks because it was hard-coded into the original program.
The block contains a headline from The Times newspaper: “The Times 03/Jan/2009 Chancellor on brink of second bailout for banks.” This message is widely interpreted as a timestamp and a comment on the financial system that Bitcoin was designed to operate alongside.
A common mix-up is calling it block 1. In ordinary counting, it is the first block, but its technical height is 0. The next block mined was block 1, created by the first transaction recipient, Hal Finney.