Gilan Province (Persian: استان گیلان‎, Ostān-e Gīlān ) is one of the 31 provinces of Iran. It lies along the Caspian Sea, just west of the province of Mazandaran, east of the province of Ardabil, north of the provinces of Zanjan and Qazvin. The northern part of the province is part of territory of South (Iranian) Talysh. At the center of the province is the main city of Rasht. Other towns in the province include Astara, Astaneh-e Ashrafiyyeh, Fuman, Lahijan, Langrud, Masouleh, Manjil, Rudbar, Roudsar, Shaft, Talesh, and Soumahe Sara.

The main harbor port of the province is Bandar-e Anzali (previously Bandar-e Pahlavi).

During the Persian era, this area was a province known as Daylam (sometimes Daylaman, Dailam or Delam). The Daylam region corresponds to the modern region of Gīlān. It was the place of origin of the Buyid dynasty. The people of the province had a prominent position during the Sassanid dynasty, their presence extended to Mesopotamia.

The first recorded encounter between Gilak and Deylamite warlords and invading Muslim Arab armies was at the Battle of Jalula in 637 AD. Deylamite commander Muta led an army of Gils, Deylamites, Azerbaijanis and people of the Rey region. Muta was killed in the battle and his defeated army managed to retreat in an orderly manner.

The Gilaki people (in Gilaki: گیلک) are an Iranian people whose homeland is the Gilan Province in northwest Iran. They are also found in the eastward neighboring province of Mazandaran. Along with the Mazandarani people, the Gilaki comprise one of the Caspian people, inhabiting the southern coastal region of the Caspian Sea. They speak the Gilaki language, which is closely related to Mazandarani. Gilaki is not a dialect of Persian, but it shares many words with it as well as with Kurdish. The Mazandarani people call their language Geleki or Gilaki but more recently call it Mazani or Mazandarani from the name of their province. ^ a b c d e f g C.S. Coon, "Iran:Demography and Ethnography" in Encycloapedia of Islam, Volme IV, E.J. Brill, pp 10,8. Excerpt: "The Lurs speak an aberrant form of Archaic Persian" See maps also on page 10 for distribution of Persian languages and dialect ^ a b c Kathryn M. Coughlin, "Muslim cultures today: a reference guide," Greenwood Publishing Group, 2006. pg 89: "...Iranians speak Persian or a Persian dialect such as Gilaki or Mazandarani"