The 1120s BC is a decade which lasted from 1129 BC to 1120 BC.

This article does not cite any sources. (September 2009)

• 1126 BC—Thymoetes, legendary King of Athens, dies childless after a reign of 8 years. He is succeeded by his designated heir Melanthus of Pylos, a fifth-generation descendant of Neleus who had reportedly assisted him in battle against the Boeotians.
• 1122 BC—Legendary founding emigration of Gija to Gija Joseon.
• 1122 BC—The Zhou dynasty is founded.
• c. 1120 BC—Destruction of Troy.