The Babylonian War was a conflict fought between 311–309 BC between Antigonus I Monophthalmus and Seleucus I Nicator, ending in a victory for Seleucus. This conflict ended any possibility of restoration of the former empire of Alexander the Great, a result confirmed in the Battle of Ipsus. The battle also marked the birth of the Seleucid Empire by giving Seleucus control over the eastern satrapies of Alexander's former territory.

Antigonus retreated and accepted that Babylonia, Media, and Elam belonged to Seleucus. The victor now moved to the east and reached the Indus valley, where he concluded a treaty with Chandragupta Maurya. The Mauryan emperor received the eastern parts of the Seleucid Empire, which included Afghanistan, Pakistan and west India, and gave Seleucus a formidable force of five hundred war elephants. By adding all of Iran and Afghanistan, Seleucus became the most powerful ruler since Alexander the Great. Restoration of Alexander's Empire was, after the Babylonian War, no longer possible. This outcome was confirmed in the Fourth War of the Diadochi and the Battle of Ipsus (301).