Alexander I was ruler of Macedon from 495 BC to 450 BC. He was the son of Amyntas I of Macedon.

According to Herodotus he was unfriendly to Persia, and had the envoys of Darius I killed when they arrived at the court of his father during the Ionian Revolt. However, he was forced to submit to Persia during the invasion of Greece by Darius' son Xerxes I, and he acted as a representative of the Persian governor Mardonius during peace negotiations after the Persian defeat at the Battle of Salamis in 480 BC. Despite his cooperation with Persia, he frequently gave supplies and advice to the Greeks, and warned them of Mardonius' plans before the Battle of Plataea in 479 BC. Alexander eventually regained Macedonia's independence after the end of the Persian Wars.

Although Macedon was considered a semi-barbaric state by other Greeks, Alexander claimed descent from Argosian Greeks, and he was permitted to participate in the Olympic Games, a great honour for a "barbarian" king. He modeled his court after Athens and was a patron of the poet Pindar.

In 450 he was succeeded by his son Perdiccas II.