Kushtia Sadar () is an upazila of Kushtia District in Khulna, Bangladesh. Kushtia Sadar Thana was formed in 1823 and it was turned into an upazila in 1983.
According to the 2022 Bangladeshi census, Kushtia Sadar Upazila had 145,478 households and a population of 560,963. 8.07% of the population were under 5 years of age. Kushtia Sadar had a literacy rate (age 7 and over) of 74.48%: 76.50% for males and 72.48% for females, and a sex ratio of 99.27 males for every 100 females. 244,152 (43.52%) lived in urban areas.
International artists have come together at Smaran Matshya Beej Khamar to participate in the annual CRACK International Art Camp since 2007.
7th National Debate Federation program (NDF) was held in Kushtia Medical College in 2019.
Kushtia Sadar Upazila is divided into Kushtia Municipality and 14 union parishads: Abdulpur, Ailchara, Alampur, Barakhada, Battail, Gosind Durgapur, Harinarayanpur, Hatas Haripur, Jiarakhi, Jhaudia, Mazampur, Monohardia, Patikabari, and Uzangram. The union parishads are subdivided into 122 mauzas and 176 villages and Kushtia Model Thana also is part of local administration as well.
Kushtia Municipality was formed in 1969. The Municipality is subdivided into 21 wards and 36 mahallas.