Damanhur (Egyptian Arabic: دمنهور Damanhūr , IPA: [dɑmɑnˈhuːɾ]; Egyptian: Dmỉ-n-Ḥr.w; Ancient Greek: Ἑρμοῦ πόλις μικρά Hermopolis Mikra ) is a city in Lower Egypt, and the capital of the Beheira Governorate. It is located 160 km (99 mi) northwest of Cairo, and 70 km (43 mi) E.S.E. of Alexandria, in the middle of the western Nile Delta.

In Ancient Egypt, the city was the capital of Lower Egypt's 7th Nome of A-ment. It stood on the banks of a canal which connected the lake Mareotis with the Canopic or most westerly arm of the Nile. The city was dedicated to the Ancient Egyptian god Horus. In Greek and Roman times, it was called Hermopolis Mikra or Hermopolis Parva, which would also give it an association with Hermes, the Egyptian Thoth. As Hermopolis, the city attracted the notice of numerous ancient geographers, including Stephanus of Byzantium s. v., Strabo (xvii. p. 802), Ptolemy (iv. 5. § 46), and the author of the Antonine Itinerary (p. 154). It is a Roman Catholic titular see.

In 1986, the population of Damanhur was 188,939. The richly cultivated Beheira province gives rise to mainly agricultural industries which include cotton ginning, potato processing, and date picking. It also has a market for cotton and rice.

Ahmed H. Zewail, who won the Nobel Prize for Chemistry in 1999, was born in Damanhur in 1946.

Damanhur was known in the ancient Egyptian scripts by the name "Dmi en Hor", which means the city of the god Hor or Horus, on the grounds that it was a center for the worship of this god. It was also known by other names: in the Egyptian texts, "Behdet"; in the Greek texts "Hermou Polis Mikra" (the lesser city of Hermes), translated to Latin by the Romans as "Hermopolis Parva"; the name "Obollenoboles" (or Apollonopolis) associated it with the Greek god Apollo, and it was also called "Tel Ballamon". Later, the Egyptians reverted to the old name, represented as "Temenhor", which after the Islamic conquest was reinterpreted in Arabic as "Damanhur", the present name.

By 14 of September 1807, a treaty of Damanhur was signed between Mohamed Ali Pasha and the English General Frasier, the chief of Military Troops were attacking the Egyptian Coast and occupying Alexandria by help of promised Al-Alfi Bic, but English troops were defeated by People of Rosetta (a Northern city 30 Klm`s east of Alexandria where Nile and Mediterranean see meets)where the troops were trapped inside the city and many English soldiers died, so The General Frasier requested to Leave Egyptian Shores without delay, which done by 14/9/1807, Damanhur treaty was the First agreement drafted in Egyptian new and modern Era.