Who discovered goldfish?

Goldfish weren't "discovered" in the sense of being found in the wild for the first time. They were actually selectively bred from a common carp species, the Prussian carp (Carassius gibelio), in China over a thousand years ago.

Therefore, there isn't a single person credited with "discovering" goldfish. Instead, it was a gradual process of selective breeding over generations that led to the beautiful, golden fish we know today.