Kaptai (Bengali: কাপ্তাই) is an upazila of Rangamati District in the Division of Chittagong, Bangladesh.

It is said that in the past, the river was wild and full of tropical flora and fauna.

Large quantities and several varieties of canes could be found along the river bank that flows from the south, upper ridge.

The Kaptai Dam, built for this purpose on the Karnaphuli River, created the Kaptai Lake, the largest man-made dam in Bangladesh.

As of the 2022 Bangladeshi census, Kaptai upazila had a population of 55,410.