Chittagong District (Bengali: চট্টগ্রাম জেলা), (Chittagonian: Sitang/Chatga), officially Chattogram District, is a district located in south-eastern Bangladesh. It is a part of the Chittagong Division. Due to its geographical location, Chittagong is classified as a special district in Bangladesh. With its hills, sea, valleys, and forests, Chittagong is one of the most naturally beautiful regions in the country. Because of its natural beauty and diversity, it is often referred to as the "Queen of the East". The commercial capital of Bangladesh and the country's only two-dimensional city are both located in Chittagong District. In terms of establishment, this is the oldest district in Bangladesh, and by area, it is the second largest. The population of Chittagong District was 9,439,076 at the 2022 Census. The district has its own distinct language and culture. Due to its linguistic and cultural uniqueness, it is considered the most diverse district in Bangladesh. The language spoken by the people of this region is known as Chatgaiya. At present, over 15 million people speak this language. Not only in Chittagong, but also in Greater Chittagong – including Cox's Bazar and the Chittagong Hill Tracts – this is the principal language of communication. Chittagong District is bordered by Cox's Bazar to the south, the Chittagong Hill Tracts to the east, Feni District and the Indian state of Tripura to the north, and the Bay of Bengal to the west. The district is also home to the second-largest sea beach in Bangladesh after Cox's Bazar, known as Banshkhali Sea Beach. In addition, the longest hanging bridge in Bangladesh is located in this Chittagong district.

Chittagong district is situated along the southeastern coast of Bangladesh, between the Bay of Bengal to the west, Cox's Bazar district to the south, the Chittagong Hill Tracts to the east, the Indian state of Tripura to the north and Feni district to the northwest. Within the Bay of Bengal is the island of Sandwip and several nearby islands, which together form an upazila of the district.

The district's topography is primarily defined by a series of low hill ranges running roughly parallel to the coast and with each other. Between these hill ranges are broad alluvial valleys with sandstone bedrock, and they are also divided by several major rivers, namely the Karnaphuli and Sangu. The most important of these ranges runs roughly from the tripoint with Feni district and Tripura in the north southeast to Chittagong city, known as the Sitakunda hills. This hill range is around 70 kilometres in length and its highest point, Chandranath, is around 350 metres in height. Along the eastern border with Khagrachhari district lies broken hill country. Another set of hills enters the district in the western part of Rangunia Upazila and ends at the Karnaphuli. South of the Karnaphuli, the hills run southeast through the eastern part of Patiya and Chandanaish upazilas to the Sangu River. South of the Sangu lies another hill range close to the coast which divides Banskhali Upazila from Satkania and Lohagara Upazilas, and continues into Cox's Bazar district. The southeastern border with Bandarban district lies along the foothills of the Hill Tracts. To the west of the hill ranges lies a coastal plain with a small width, and along the shore there are numerous beaches which have become tourist destinations.

The major rivers running through Chittagong district are the Feni, Karnaphuli and Sangu.

The Feni arises in Tripura state, and forms the entire border between Tripura and Chittagong district. It separates the Sitakunda hill range from the hill ranges in Tripura to the north. After fully entering Bangladesh, it flows southwest, meandering slightly, roughly along the border between Mirsharai Upazila with Feni district before entering the Bay of Bengal amid tidal flats.

The Karnaphuli enters Chittagong district at Chandraghona in Rangunia Upazila. It goes through several large meanders and divides the Patiya hill range from the hills to their north. It flows west before turning southwest near Boalkhali and forms the southern limits of Chittagong city, entering the sea near Patenga thana. One of its main tributaries is the Halda river. The Halda arises in the Chittagong Hill tracts and flows west into Fatikchhari Upazila. It then turns southeast, flowing past Fatikchhari and Hathazari before entering the Karnaphuli near the northeasternmost part of Chittagong city.

The Sangu river arises in Bandarban district of the Chittagong Hill Tracts, and enters Chittagong district at Dhopachari in Chandanaish Upazila. It forms most of the border between Chandanaish and Satkania upazilas, as well as between Anowara and Banshkhali upazilas, before entering the sea 16 kilometres south of the mouth of the Karnaphulil.

There are several khals also in the district.