Alexander the Great (Greek: Ἀλέξανδρος ὁ Μέγας or Μέγας Ἀλέξανδρος, Mégas Aléxandros; 356 BC – 323 BC), also known as Alexander III of Macedon (Ἀλέξανδρος Γ' ὁ Μακεδών) was an ancient Greek King (basileus) of Macedon (336–323 BC). He was one of the most successful military commanders of all time and is presumed undefeated in battle. By the time of his death, he had conquered (see Wars of Alexander the Great) the Achaemenid Persian Empire, adding it to Macedon's European territories; according to some modern writers, this was most of the world as known to the ancient Greeks.
Alexander assumed the kingship of Macedon following the death of his father Philip II, who had unified most of the city-states of mainland Greece under Macedonian hegemony in a federation called the League of Corinth. After reconfirming Macedonian rule by quashing a rebellion of southern Greek city-states and staging a short but bloody excursion against Macedon's northern neighbours, Alexander set out east against the Persian Empire, which he defeated and overthrew. His conquests included Anatolia, the Levant, Egypt, Bactria and Mesopotamia, and he extended the boundaries of his own empire as far as Punjab, India.
Alexander had already made plans prior to his death for military and mercantile expansions into the Arabian peninsula, after which he was to turn his armies to the west (Carthage, Rome and the Iberian Peninsula). His original vision, however, had been to the east, to the ends of the world and the Great Outer Sea, as described by his boyhood tutor and mentor Aristotle.