The National Iranian South Oilfields Company (NISOC) (Persian: شرکت ملی مناطق نفت‌خیز جنوب ایران, Shirkat-e Mily-e Minatâq-e Nuftxiz-e Jinvâb-e Iran) is a government-owned corporation under the direction of the Ministry of Petroleum of Iran, and operates as a subsidiary of National Iranian Oil Company.

NISOC was incorporated in 1971 in Masjed Soleyman, Khouzestan as Oil Service Company of Iran (OSCO).

[5] National Iranian South Oilfields Company, through its subsidiaries, produces crude oil, gas, and liquefied gases.

The company's reserves portfolio include Ahvaz Field (the world's 3rd largest oil field) and in charge of onshore giant oilfields in Iran (like Gachsaran, Marun, Bibi Hakimeh, RagSefid and Aghajari) and focuses on onshore upstream activity in the province of Khuzestan, Kohgiluyeh and Boyer-Ahmad, Bushehr and Ilam.

[6] As Khuzestan is the main oil- and gas-producing province, this entity is among the most significant in the NIOC subsidiaries.