The Bitcoin Whitepaper by Satoshi Nakamoto.

Satoshi Nakamoto is a pseudonym for the person who created the Bitcoin algorithm and wrote this whitepaper.

No one knows who the real Satoshi Nakamoto is. Some imposters have tried to do it in the past (Google -Craig Wright) but none have been able to prove themselves as the one.

Here is the PDF link to the white paper.

Here is the website where you will find the whitepaper in many other languages in addition to english.

P.S. Do read this whitepaper before you invest in Bitcoin.