Africa, not very far back at all. . . still going on in many places. American South, not very far either. Central America, not much earlier. In Europe, there were still slaves in Britain in Christian times, in the rest of Europe you have to go back a bit further. But of course there were slaves everywhere the Roman Empire extended, and before that the Greeks and Egyptians.
But yes, it's just a matter of how far back you have to go.
In the time of St. Patrick "British slave girl" was a unit of currency, equivelent to three cows.
FWIW, India, SE Asia, China and Japan all had slaves at different times in their history.
Then you can get into some interesting distinctions about what is slavery and what isn't. Serfdom, for instance, shades into slavery, and the word slavery itself covers a remarkable range of institutions.
In the glory period of the Ottoman Empire, for instance, the most powerful and wealthy men in the Empire, who ran the entire government and military (a distinction without much difference in the Empire) were the slaves of the Sultan.