The Decree of Canopus is a trilingual inscription in Egyptian hieroglyphs, Demotic and Greek. It commemorates a great assembly of priests held at Canopus to honour Ptolemy III Euergetes, his wife Queen Berenice and Princess Berenice. It is the second earliest instance of a series of trilingual inscriptions, the most famous example of which is the Rosetta Stone.

This round-topped stela is decorated with a frieze of stars that runs around the top of the stela’s lunette. It depicts a winged sun-disk with pendant uraei and shen-ring (symbol of infinity) hanging from their bodies beside the names of Horus Behedet and the cartouches of the king and the queen. Below is a register containing sixteen divinities and kings facing to the centre (eight on each side), where the innermost figure on the proper right side is Ptolemy III. Beneath are one hundred and ten horizontal lines of inscription; the top twenty-six of which are in hieroglyphs; the second twenty are in the Demotic script, while the final sixty-four are in Greek. The inscription describes various subjects such as military campaigns, famine, governmental organisation and Egyptian religion in Ptolemaic Egypt. It mentions the king’s donations to the temples and his support for the Apis and Mnevis (Mer-wer) cults. It declares the deceased princess Berenike as a goddess and creates a cult for her. Finally, it orders the decree to be incised in stone or bronze in both hieroglyphs and Greek, and to be displayed in the temples.

This stela inaugurates the most accurate solar calendar known to the ancient world, with three hundred and sixty-five and quarter days per year. The upper-right corner of the stela is missing a piece, and the right edge of it is damaged.