Alexander III of Macedon (20/21 July 356 – 10/11 June 323 BC), commonly known asAlexander the Great was a king of Macedon, a state in northern ancient Greece. Born in Pella in 356 BC, Alexander was tutored by Aristotle until the age of 16. By the age of thirty, he had created one of the largest empires of the ancient world, stretching from the Ionian Sea to the Himalayas. He was undefeated in battle and is considered one of history's most successful commanders.
Alexander succeeded his father, Philip II of Macedon, to the throne in 336 BC after Philip was assassinated. Upon Philip's death, Alexander inherited a strong kingdom and an experienced army. He was awarded the generalship of Greece and used this authority to launch his father's military expansion plans. In 334 BC, he invaded Persian-ruled Asia Minor and began a series of campaigns that lasted ten years. Alexander broke the power of Persia in a series of decisive battles, most notably the battles of Issus and Gaugamela. He subsequently overthrew the Persian King Darius III and conquered the entirety of thePersian Empire.At that point, his empire stretched from the Adriatic Sea to the Indus River.

Seeking to reach the "ends of the world and the Great Outer Sea", he invaded India in 326 BC, but was eventually forced to turn back at the demand of his troops. Alexander died in Babylon in 323 BC, without executing a series of planned campaigns that would have begun with an invasion of Arabia. In the years following his death, a series of civil wars tore his empire apart, resulting in several states ruled by the Diadochi, Alexander's surviving generals and heirs.

Alexander's legacy includes the cultural diffusion his conquests engendered. He founded some twenty cities that bore his name, most notably Alexandria in Egypt. Alexander's settlement of Greek colonists and the resulting spread of Greek culture in the east resulted in a new Hellenistic civilization, aspects of which were still evident in the traditions of theByzantine Empire in the mid-15th century. Alexander became legendary as a classical hero in the mold of Achilles, and he features prominently in the history and myth of Greek and non-Greek cultures. He became the measure against which military leaders compared themselves, and military academies throughout the world still teach his tactics.