Sapahar Upazila () is an upazila of Naogaon District in the Division of Rajshahi, Bangladesh.
Sapahar is located at 25.1250ðN 88.5819ðE. It has 36,232 households and total area 244.48 km<sup>2</sup>.
Sapahar Upazila is bounded by Tapan CD Block in Dakshin Dinajpur district, West Bengal, India, on the north, Patnitala Upazila on the east, Porsha Upazila on the south, and Bamangola CD Block, in Malda district, West Bengal, on the west. Main river Punarbhaba at Patari village and Jabai Beel are notable.
According to the 2022 Bangladeshi census, Sapahar Upazila had 47,718 households and a population of 184,817. 9.70% of the population were under 5 years of age. Sapahar had a literacy rate (age 7 and over) of 73.11%: 73.76% for males and 72.46% for females, and a sex ratio of 100.12 males for every 100 females. 18,480 (10.00%) lived in urban areas. Ethnic population is 4,909 (2.66%), of which Oraon are 2,058 and Santal are 1320.
According to the 2011 Census of Bangladesh, Sapahar Upazila had 36,232 households and a population of 161,792. 34,245 (21.17%) were under 10 years of age. Sapahar had a literacy rate (age 7 and over) of 42.19%, compared to the national average of 51.8%, and a sex ratio of 990 females per 1000 males. 12,696 (7.85%) lived in urban areas. Ethnic population was 5,520 (3.41%), of which Santal were 1,851, Oraon 1,568 and Barman 796.
Most of the people of the Sapahar Upazila depends on agriculture for a living. The main corps are mango, paddy, wheat, mustard, and vegetables.
Sapahar Thana was formed in 1979. It was turned into an upazila in 1985.
The Upazila is divided into six union parishads: Aihai, Goala, Pathari, Sapahar, Shiranti, and Tilna. The union parishads are subdivided into 151 mauzas and 232 villages.
Sapahar Sadar Town covers an area of . The town area consists of ward no. 1, 2, 4 and partially 3. According to the census of 2011, It has a population of 12696. About 2924 households are situated here.
Tertiary educational institutions in Sapahar include: