While it's impossible to say who *discovered* Jupiter in the sense of being the first human to ever see it, Jupiter has been known since ancient times.

The ancient Babylonians were among the first to observe and record the planet, dating back to at least the 7th century BC. They called it "Marduk" after their chief god.

The ancient Greeks also observed Jupiter and named it after their king of the gods, Zeus.

So, rather than one specific discoverer, Jupiter has been observed and known throughout history, with multiple ancient civilizations noting its presence in the night sky.