Delduar () is an upazila of Tangail District in the Division of Dhaka, Bangladesh.
Delduar is located at . It has 48,227 households and total area 184.54 km<sup>2</sup>.
According to the 2022 Bangladeshi census, Delduar Upazila had 56,971 households and a population of 218,745. 8.12% of the population were under 5 years of age. Delduar had a literacy rate (age 7 and over) of 71.75%: 74.64% for males and 69.27% for females, and a sex ratio of 88.15 males for every 100 females. 30,267 (13.84%) lived in urban areas.
According to the 2011 Census of Bangladesh, Delduar Upazila had 48,227 households and a population of 207,278. 41,018 (19.79%) were under 10 years of age. Delduar had a literacy rate (age 7 and over) of 51.57%, compared to the national average of 51.8%, and a sex ratio of 1060 females per 1000 males. 14,102 (6.80%) lived in urban areas.
Delduar Upazila is divided into eight union parishads: Atia, Delduar, Deoli, Dubail, Elashin, Fazilhati, Lauhati, and Pathrail. The union parishads are subdivided into 123 mauzas and 162 villages.