Khulna (Bengali: খুলনা, pronounced [ˈkʰulna] ^ⓘ) is the third-largest city in Bangladesh, after Dhaka and Chittagong. It is the administrative centre of the Khulna District and the Khulna Division. It is the divisional centre of 10 districts of the division. Khulna is also the second largest port city of Bangladesh after Chittagong because of Port of Mongla. There is also a river port within the city named Port of Khulna. Khulna's economy is mainly marine, sea port and local industry based and it is the third-largest in Bangladesh.

Khulna is on the Rupsha and Bhairab River, a strategic industrial point in southwestern Bangladesh. It is also an important industrial hub in Bangladeshi industry, hosting many of the nation's largest companies. Khulna's economy is affected by the Port of Mongla, Bangladesh's second-largest seaport.

A colonial steamboat service, which includes the Tern, Osrich and Lepcha, operates on the river route to the city. Khulna is considered the gateway to the Sundarbans, the world's largest mangrove forest and home of the Bengal tiger. It is north of the Mosque City of Bagerhat, a UNESCO World Heritage Site.

Khulna was part of the ancient kingdoms of Vanga, Gangaridai and Samatata. After the end of the Pala Empire, it was ruled by the Sena dynasty during the 12th-century reign of Ballala Sena, and formed part of the Bagri division of Bengal. During the 14th century, Shamsuddin Firoz Shah was the first Muslim ruler to arrive in the city. Muslim settlements increased during the time of Shamsuddin Ilyas Shah, and many mosques and shrines were established. A Muslim saint, Khan Jahan Ali, acquired a jagir (fiefdom) encompassing a large part of Khulna Division from the king of Gauḍa during the 15th century and renamed the region as Jahanabad. Ali ruled until he died in 1459.

After Ali's death, the city became part of the Bengal Sultanate. During the reign of Daud Khan Karrani in the 16th century, Vikramaditya (one of Karrani's chief ministers) obtained a grant in southern Bengal—including Khulna—when Karrani was fighting the Mughals. Vikramaditya established a sovereign kingdom with its capital at Iswaripur (in present-day Satkhira District). He was succeeded by his son, Pratapaditya, who gained preeminence over the Baro-Bhuyans and controlled southern Bengal. Vikramaditya was defeated by Raja Man Singh I, a Hindu Rajput general of the Mughal emperor Akbar, in 1611.

Khulna was ruled by autonomous Bengali nawabs until 1793 when the British East India Company abolished nizamat (local rule) and took control of the city. Becoming part of Jessore District in 1842, it became the headquarters of Khulna District (the Khulna and Bagerhat subdivisions of Jashore District, the Satkhira subdivision of 24 Parganas district, and the Sundarbans) in 1882. Khulna had a pouroshava (municipal council) in 1884, which became a municipal corporation in 1984.

Before 19 August 1947, Khulna District was part of undivided Bengal. Khulna first declared itself as part of India in 1947, and the Indian flag was flown on 15 August. Syed Mohammad Abdul Halim (an official of the Bengali civil service) requested Khulna's inclusion in Pakistan, and the boundary commission declared that the city was part of East Bengal. Sher e Bangla A.K.Fazlul Haq, Muslim League leaders Khan A Sabur, Advocate Hamidul Haq Chowdhury, A. F. M. Abdul Jalil, and Abdul Mojid Khan were also involved in the process.

During the Bangladesh Liberation War, the Pakistan Army created the 314th ad hoc Brigade to hold Khulna. The city's Mukti Bahini fighters were part of sector 8 under the command of Major Abu Osman Chowdhury and, later, under Major Mohammad Abdul Monjur.