Chhagalnaiya is an upazila of Feni District in the Division of Chittagong, Bangladesh.

Feni is a coastal district situated in the south-east of Bangladesh, within the Chittagong Division. One of Bangladesh's smallest districts, it is strategically located along the Dhaka–Chittagong transportation corridor. Bordered by India to the north and the Bay of Bengal to the south, it serves as the sole entry point linking Chittagong, the country's primary port city, to the northern districts.