"Capitalism" as a feature, or as the defining system of organizing a society? I discussed the topic at length in one of my first threads on this forum which might interest you, and I also write this more recent post for a similar question, but I think that ultimately u/Tiako offered the best explanation in the earliest days of this subreddit's life.

I can offer a few additional ideas and maybe some quick clarifications in addition to the linked answers above which might also interest you:

If by "Capitalism" we mean the mere existence of private enterprise, then we have to look no further than the collapse of the Mycenaean "Palace Economy" and trace the seafaring routes of ancient merchants as early as the Bronze and Iron age. In this definition, "Capitalism" is more of a feature of an economy, rather than an organized system, and is probably closest to the use of the word in contemporary media.

If instead we mean a "Society organized by and for owners of capital," the traditional answer (given by Schumpeter but also alluded to by Marx) is in Italian cities sometime in the twelfth century, although capitalism by this definition would spread in ebbs and flows over the years and centuries, meaning that the adoption of a "Capitalist" system by this definition was not linear, and therefore kind of pointless to pinpoint.

If instead you mean the earliest definition of the word, referring a western european society principally organized around capital ownership as commented on by the early Marxo-communist writers, the answer is sometime in the 19th century (although modern economic historians would prefer to trace roots running as much as a century earlier, even if they are looking through a marxist lens).