Basail () is an upazila of Tangail District in the Division of Dhaka, Bangladesh.
Basail is located at . It has 38,565 households and total area 157.77 km<sup>2</sup>.
According to the 2022 Bangladeshi census, Basail Upazila had 49,024 households and a population of 188,936. 7.89% of the population were under 5 years of age. Basail had a literacy rate (age 7 and over) of 73.98%: 77.72% for males and 70.59% for females, and a sex ratio of 92.13 males for every 100 females. 50,594 (26.78%) lived in urban areas.
According to the 2011 Census of Bangladesh, Basail Upazila had 38,565 households and a population of 159,870. 32,219 (20.15%) were under 10 years of age. Basail had a literacy rate (age 7 and over) of 50.43%, compared to the national average of 51.8%, and a sex ratio of 1125 females per 1000 males. 13,496 (8.44%) lived in urban areas.
Basail Upazila is divided into six union parishads: Basail, Fulki, Habla, Kanchanpur, Kaoaljani, and Kashil. The union parishads are subdivided into 72 mauzas and 107 villages.
According to Banglapedia, Basail Govinda Government High School, founded in 1945, is a notable secondary school.
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