Gilan Province (Persian:اُستان گیلان‎‎, Ostān-e Gīlān, also Latinized as Guilan) 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 also borders the Republic of Azerbaijan in the north, as well as Russia across the Caspian Sea.