Karaj (Persian: کرج; pronounced [kæˈɾædʒ] ) is a city in the Central District of Karaj County, Alborz province, Iran, serving as capital of the province, the county, and the district. The earliest records of Karaj date back to the 30th century BC. The city was developed under the rule of the Safavid and Qajar Empire and is home to historical buildings and memorials from those eras. This city has a unique climate due to access to natural resources such as many trees, rivers, and green plains. After Tehran, Karaj is the largest immigrant-friendly city in Iran, so it has been nicknamed "Little Iran."
Although the county hosts a population around 1.97 million, as recorded in the 2016 census, most of the 1,419 km2 (548 sq mi) county is rugged mountain. The urban area is the fourth-largest in Iran, after Tehran, Mashhad, and Isfahan. Eshtehard County and Fardis County were split off from Karaj County since the previous census.