Hamadan is among the oldest cities of Iran. Medes chose Hamadan- which was then called Hegmataneh- as their capital, but the results of studies indicate that Hegmataneh city has existed before being elected as the capital by Medes and also a group of Kassites people lived there. Later the survivors of Kassites have created the nation called Mede together with a group of Aryan people, and established the Medes State by overcoming the aggressor Assyrian State and have placed Karkashi as their capital and since then, this city has been named Hegmataneh. Hamadan has always been regarded as one of the major centers of the Jewish settlement in Iran, but most inhabitants of Hamadan are Shiite Muslims.
Hamadan has been the first capital of the first monarchy in Iran 2550 to 2700 years ago. The first king of the Medes established the city and it was called Hegmataneh meaning "place of aggregation" in the language of Iranians during Medes period. Hamadan has also been the summer capital of the Achaemenid and Parthian kings. Gradually, in the Sassanid period the name Hegmataneh has been changed to Ahamatan/ Ahamadan and thereafter to Hamadan. The works discovered in Hegmataneh archaeological enclosure as well as Ganjnameh inscriptions belong to that time.
The immigration of originally Aryan peoples since about 2500 years ago to the western part of Iran and the present limits of Hamadan province gradually led to the formation of the first inclusive State having Hegmataneh (Hamadan) as its center in the Iranian plateau. In 650 B.C this State, enjoying its maximum authority expanded its territory on the east to the Middle Asia and on the west to the small Asia while conquering over the greatest political and military power of that period, i.e. the Assyrian State. Based on the writings of the Greek historian Herodotus, massive fortifications including 7 involute fortresses and royal palaces were erected in their capital Hegmataneh (Hamadan) by the order of Diaco, the first king of the Medes. Most scholars of the history and archeology believe that the present hills and buildings of Hegmataneh in the heart of the city of Hamadan are remnants of those installations. A considerable number of gold and silver objects and the remains of stone palaces have remained in memoriam in addition to the stone cuneiform writings of Hamadan Ganjnameh from the Achaemenid period and those interested may visit them at the State National Museum and the hill of Hegmataneh Museum. The Parthian cemetery in Hamadan and Anahita Temple in Nahavand are left from the Seleucid and Parthian eras.
In the Sassanid era, Hamadan was one of the mints of that government and various coins belonging to that period are available. City of Nahavand also had a special importance at this time and a fortified stronghold located in it and it was one of the centers of the seven states where field marshals stayed during this period.
When Arabs attacked Iran they called the conquest of Nahavand the great victory and they regarded the opening of Hamadan in 645 AD after the conquest of Nahavand as their greatest triumph over the Sassanians. Ghale Jugh cave in Famenin and the remains of a castle in the same place may be mentioned among the works of that era.
Various monuments belonging to this post-Islam era are also left in different points of the province the most important of which include: The very beautiful and valuable building of Alavian Dome of the Seljuk era – Ghorban Tower - Tomb of Esther and Mordechai – Khezr mausoleum from centuries 7 to 9 AH in Hamadan- Imamzadeh Aznav from the Seljuk era in Famenin – Imamzadeh Houd and Azhar in Razan and the mausoleum of the prophet Habakkuk in Tuyserkan of the eighth century -Imamzadeh Yahya - Imamzadeh Hussein and Imamzadeh Ismail in Hamadan and Farasfaj inn and the seminary of Sheikh Ali khan Zanganeh in Tuyserkan - water reservoir and a petroglyph known as Aghajan Balaghi inscription related to the structure of a dam in Asadabad – Mirfattah Icehouse in Malayer and Haj Agha Torab bathhouse in Nahavand as well as a number of bridges, including broken bridge (Khosroabad) in Asdabad- Kurijan and Abshineh bridge in Hamadan- Jahanabad bridge in Famenin- - Paul Farasfaj bridge and bazar complex in Tuyserkan and Zaramin bridge in Nahavand of the Safavid era and the bazar, mosque and Imam square of Hamadan and the bazar of Malayer among the important buildings after the Safavid.
The people of Hamadan speak Persian with a Hamadanian dialect.