Gaibandha Sadar () is an upazila of Gaibandha District in Rangpur Division, Bangladesh.
Gaibandha Sadar is located at . It has 109,628 households and a total area of 324.05 km<sup>2</sup>.
According to the 2022 Bangladeshi census, Gaibandha Sadar Upazila had 131,599 households and a population of 499,196. 9.73% of the population were under 5 years of age. Gaibandha Sadar had a literacy rate (age 7 and over) of 70.30%: 73.10% for males and 67.72% for females, and a sex ratio of 93.25 males for every 100 females. 131,891 (26.42%) lived in urban areas.
According to the 2011 Census of Bangladesh, Gaibandha Sadar Upazila had 109,628 households and a population of 437,268. 105,798 (24.20%) were under 10 years of age. Gaibandha Sadar had a literacy rate (age 7 and over) of 47.50%, compared to the national average of 51.8%, and a sex ratio of 1,045 females per 1,000 males. 94,089 (21.52%) lived in urban areas.
According to the 1991 Bangladesh census, Gaibandha Sadar had a population of 359,226, of whom 172,249 were aged 18 or over. Males constituted 50.6% of the population, and females 49.4%. Gaibandha Sadar had an average literacy rate of 28.2% (7+ years), against the national average of 32.4% .
Gaibandha Sadar Upazila is divided into Gaibandha Municipality and 13 union parishads: Badiakhali, Ballamjhar, Boali, Ghagoa, Gidari, Kamarjani, Kholahati, Kuptola, Laxmipur, Malibari, Mollarchar, Ramchandrapur, and Shahapara. The union parishads are subdivided into 130 mauzas and 144 villages.
Gaibandha Municipality is subdivided into 9 wards and 35 mahallas.
According to Banglapedia, Gaibandha Government Boys' High School, founded in 1885, is a notable secondary school.