The Central District of Karaj County () is in Alborz province, Iran. Its capital is the city of Karaj.
In 2010, the county was separated from Tehran province in the establishment of Alborz province. In 2013, the city of Meshkin Dasht, the Fardis neighborhood in the city of Karaj, and other parts of the district were separated from it in establishing Fardis County.
At the time of the 2006 National Census, the district's population (as a part of Tehran province) was 1,667,024, in 460,242 households. The 2016 census measured the population of the district as 1,956,267 people in 617,773 households.