Gilan Province is one of the 31 provinces of Iran. It lies along the Caspian Sea, in Iran's Region 3, west of the province of Mazandaran, east of the province of Ardabil, and north of the provinces of Zanjan and Qazvin. It borders the Republic of Azerbaijan in the north and Russia across the Caspian Sea.
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, Rudsar, Shaft, Hashtpar(city), and Sowme'eh Sara. The main harbor port is Bandar-e Anzali (previously Bandar-e Pahlavi).
Gilan has a humid subtropical climate with, by a large margin, the heaviest rainfall in Iran: reaching as high as 1,900 millimetres (75 in) in the southwestern coast and generally around 1,400 millimetres (55 in). Rasht, the capital of the province, is known internationally as the "City of Silver Rains" and in Iran as the "City of Rain".