The natural harbour of Chattogram is an ancient gateway to the region of Bengal. It was noted as one of the largest Eastern ports by the Roman geographer Ptolemy in the 1st century. As part of the rich seafaring tradition of the Bengali people, coastal Chattogram was settled and ruled by different regional kingdoms. Arab traders saw well-developed currency, banking and shipping in Chattogram during the 9th century. Early cosmopolitan Muslims established dominance over the port as an entrepot of maritime trade, while Arakan, Bengal and Tripura competed for control of the wider hinterland. Chattogram became the principal port of the Bengal Sultanate. It was used by several leading medieval global explorers, including Ibn Battuta and Niccolò de’ Conti. Later, Mrauk U, with assistance from Portuguese trading posts, gained control of the area. The Mughal conquest of Chattogram re-established Bengali control and ushered an era of stability and trade. The city was renamed as Islamabad. This diverse history is reflected in the rural Chittagonian dialect of Bengali, which has a nearly 50% Arabic-origin vocabulary, as well as Persian and Portuguese loanwords.

Ceded to the British East India Company in 1760, Chattogram became the chief port of Eastern Bengal and Assam under the British Raj, as well as a hub of railways. A notable anti-colonial uprising took place in 1930. It was an important base for Allied Forces during the Burma Campaign in World War II. Rapid industrialization followed the war, as Chattogram became part of East Pakistan. During the Bangladesh liberation war in 1971, Chattogram was site of the country’s declaration of independence.

Modern Chattogram is an important economic hub in South Asia. It is home to the Chattogram Stock Exchange and many of Bangladesh’s oldest and largest companies. The Port of Chattogram is the largest international seaport on the Bay of Bengal. It is the largest base of the Bangladesh Navy.

Chattogram has a population of more than 2.5 million and its Metropolitan Area has a population of 4,009,423.By gender, the population was 54.36% male and 45.64% female, and the literacy rate in the city was 60 percent, in 2002.Muslims at 86% form the overwhelming majority of the population and rest being 12% Hindus and 2% other religions.

The city also has many ethnic minorities, especially members of indigenous groups from the frontier hills of Chattogram Division, including Chakmas, Rakhines and Tripuris; as well as Rohingya refugees. The Bengali-speaking Theravada Buddhists of the area, known as Baruas, are one of the oldest communities in Chattogram and one of the last remnants of Buddhism in Bangladesh. Descendants of Portuguese settlers, often known as Firingis, also live in Chattogram, as well as Catholics, who largely live in the old Portuguese enclave of Paterghatta. There is also a small Urdu-speaking Bihari community living in the ethnic enclave known as Bihari Colony.

Chattogram has been a seaport since ancient times. The region was home to the ancient Bengali Buddhist Samatata and Harikela states. It later fell under of the rule of the Gupta Empire, the Pala Empire and the Vesali kingdom of Arakan till the 7th century. Arabs traded with the port from the 9th century AD. An account by historian Lama Taranath has revealed a Buddhist king Gopichandra had his capital at Chattogram in the 10th century, and according to Tibetan tradition, Chattogram was the birthplace of 10th century Buddhist Tantric Tilayogi.

Sultan Fakhruddin Mubarak Shah of Sonargaon conquered Chattogram in 1340 AD.Sultan Giasuddin Mubarak Shah constructed a highway from Chattogram to Chandpur and ordered the construction of many lavish mosques and tombs. After the defeat of Mahmud Shah in the hands of Sher Shah in 1538, the Arakanese Kingdom of Mrauk U regained Chattogram. From this time onward, until its conquest by the Mughals, this region was under the control of the Portuguese and the Magh pirates (a notorious name for Arakanese) for 128 years.

After the Arakanese expulsion, Islamabad, as the area came to be known, made great strides in economic progress. What is called Chattogram today also began to have improved connections with the rest of Mughal Bengal. The city was occupied by Burmese troops shortly in First Anglo-Burmese War in 1824 and the British increasingly grew active in the region and it fell under the British Empire. The people of Chattogram made several attempts to gain independence from the British, notably on 18 November 1857 when the 2nd, 3rd, and 4th companies of the 34th Bengal Infantry Regiment stationed at Chattogram rose in rebellion and released all the prisoners from jail but were suppressed by the Kuki scouts and the Sylhet Light Infantry (10th Gurkha Rifles).