Aligarh district (Hindi pronunciation: [əliːgəɽʱ]) is one of the 75 districts in the northern Indian state of Uttar Pradesh. This district is a part of Aligarh Division. The districts which adjoin Aligarh are (clockwise from north) Gautam Buddha Nagar, Bulandshahr, Sambhal, Badaun, Kasganj, Hathras and Mathura of Uttar Pradesh and Palwal district of Haryana.

According to the 2011 census, Aligarh district has a population of 3,673,889, roughly equal to the nation of Mauritania or the US state of Oklahoma. This gives the district a ranking of 76th in India (out of a total of 640 districts). The district has a population density of 100 inhabitants per square kilometre (260/sq mi). Its population growth rate over the 2001-2011 decade was 22.78%. Aligarh has a sex ratio of 876 females for every 1,000 males, and a literacy rate of 69.61%. 33.13% of the population lived in urban areas. Scheduled Castes make up 20.56% of the population.

At the time of the 2011 Census of India, 92.54% of the population in the district spoke Hindi, 5.34% Urdu and 1.90% Braj bhasha as their first language. The local language is Braj bhasha.

In 1941 to 1991 Census Aligarh District Includes the following tehsils

Following Creation of Hathras District In 1997 Hathras, Sikandra Rao, Iglas. Later Iglas was again returned to Aligarh District.