Dezful (Persian: دزفول; pronounced [dɛzˈfuːl]) is a city in the Central District of Dezful County, Khuzestan province, Iran, serving as capital of both the county and the district.

Dezful is one of Khuzestan province's oldest cities. According to Walther Hinz excavations, Awan (capital of the first dynasty of Elam, the Awan dynasty) was located in Dezful.

The name Dezfūl is believed to be associated with a Sasanian bridge constructed over the Āb-e Dez by Shapur II. The Sasanians also built a fortress in close proximity to protect the bridge. This area, encompassing the bridge and the fortress, eventually evolved into the city of Dež-Pol or Dezfūl, although this name was not commonly used until the 12th century. In the 10th century, the writer Eṣṭaḵrī referred to it as Qanṭarat-al-Andāmeš. It was also known as Qaṣr al-Rūnāš. The stone foundation of the bridge is still visible, while the upper part underwent several brick reconstructions during the early Islamic, Saljuq, and Qajar periods. In the 14th century, Ḥamd-Allāh Mostāwfī described it as 520 paces long and 15 paces wide, with forty-two arches. Šaraf-al-Dīn Yazdī, who visited the area in 795/1393, also provided a detailed description.

According to George Curzon, who visited the area in the late 19th century, the principal local industry in Dezfūl was indigo, with 120 factories in the town. The cultivation of indigo was introduced in the early 19th century. Dezfūl was also renowned for its fine reed pens.

The name Dezful has been derived from the two words dej (fortress) + pul (bridge), which in combination could stand for 'the bridge to the fortress' or 'fortified bridge' in Persian language. The original name of the city was Dezhpul, but after the Muslim conquest of Persia, the city was renamed Dezful, since the Arabic language does not have 'p' and 'zh' sounds. The city is also known as Dizful and Desful.

The people of Dezful, known as Dezfuli, Dezfoolian or Dezfulian, speak Dezfuli – a dialect distinct to Dezful – and Shushtari, a dialect of Shushtar that is sometimes considered to be one of the most archaic dialects spoken in the Iranian plateau, and by others as a dialect of the Persian language. These dialects belong to the Southwest Iranian language group. However, they differ significantly from standard Persian in terms of pronunciation, word formation, and vocabulary. The most notable distinctions are found in the structure of verbs. Although they share some similarities with nearby Lor dialects, they are still distinct. The differences between Dezfuli and Shushtari are mainly a result of variations in the detailed sound patterns of the language.

Historically, Dezful was home to a Mandaean community for many centuries. One of Dezful's best-known residents was the Mandaean priest Ram Zihrun.

At the time of the 2006 National Census, the city's population was 228,507 in 55,711 households. The following census in 2011 counted 248,380 people in 66,715 households. The 2016 census measured the population of the city as 264,709 people in 78,348 households.