The siege of Naxos (499 BC) was an unsuccessful Persian backed attempt to restore a part of exiled Naxian aristocrats. The failure of the attack played a part in the outbreak of the Ionian Revolt (499-494 BC), an attempt to overthrow Persian control of the Greek cities of Ionian.
In 500 BC a group of exiled aristocrats from Naxos attempted to enlist the support of Aristagoras, tyrant of Miletus (then part of the Persian Empire). Aristagoras wanted to support the exiles, but knew that he didn't have the military power to succeed by himself, and so he approached Artaphernes, satrap of Lydia. Artaphernes was quickly won over, and won the support of the Emperor Darius I. Possession of Naxos would give the Persians a foothold in the Cyclades.
Darius appointed his cousin Megabates to command the expedition. A fleet of 200 triremes was gathered from the Greek cities in the area, and a Persian army was provided. The fleet set sail in 499 BC, and moved to Chios. It was then stuck for a month while it waited for a north wind, and during this period Aristagoras and Megabates fell out. According to Herodotus Megabates warned the Naxians about the upcoming attack, and they were ready and waiting when the fleet finally arrived. This story may not be true, as Megabates was still recorded as a Persian admiral several years later.
The attackers persisted with the siege for four months, but eventually they ran out of supplies and had to abandon the siege. They did build a stronghold on the island for the Naxian exiles before they left. In the aftermath of this failure Aristagoras decided to launch a revolt against Persian power, possibly to save himself from Persian retribution. The resulting Ionian Revolt lasted from 499 to 494 BC, but was eventually crushed by the Persians.