What is the oldest edition of D&D?

I'm curious, could you enlighten me on the earliest iteration of Dungeons & Dragons? Specifically, I'm looking for the name or designation of the very first edition that was released. It's fascinating to trace the roots of such a beloved and enduring game, and I'm eager to learn more about its humble beginnings. So, what exactly is the oldest edition of D&D that has been recorded in history?