Which Persian emperor was defeated by athenian forces at the battle of marathon?

The Persian emperor defeated by Athenian forces at the Battle of Marathon in 490 BCE was Darius I. This battle was a significant event in the Greco-Persian Wars, marking the first major victory for the Athenians against the Persians. Darius sought to expand his empire into Greece but faced unexpected resistance from the Athenians, who won despite being outnumbered.