Kamalnagar () is an upazila of Lakshmipur District in the division of Chittagong, Bangladesh.
Kamalnagar Upazila is divided into nine union parishads: Char Folcon, Char Kadira, Char Kalkini, Char Lawrench, Char Martin, Hajirhat, Patarirhat, Shaheberhat, and Torabgonj. The union parishads are subdivided into 33 mauzas and 33 villages.
According to the 2022 Bangladeshi census, Kamalnagar Upazila had 51,219 households and a population of 217,293. 12.45% of the population were under 5 years of age. Kamalnagar had a literacy rate (age 7 and over) of 62.65%: 62.13% for males and 63.13% for females, and a sex ratio of 95.29 males for every 100 females. 54,014 (24.86%) lived in urban areas.
According to the 2011 Census of Bangladesh, Kamalnagar Upazila had 46,092 households and a population of 222,915. 69,319 (31.10%) were under 10 years of age. Kamalnagar had a literacy rate (age 7 and over) of 30.7%, compared to the national average of 51.8%, and a sex ratio of 1004 females per 1000 males. 12,747 (5.72%) lived in urban areas.