Nuristān (Persian:نورستان), also spelled Nurestān or Nooristan, is a region in Afghanistan embedded in the south of the Hindu Kush valleys. Its administrative center is Parun. It was formerly known as Kafiristan ("land of the unbelievers") until the inhabitants were converted to Islam in 1896, and thence the region has become known as Nuristan ("Land of Light").

Today it is one of the thirty-four provinces of Afghanistan, formed in 1989 and officially established in 2001 from the northern parts of Laghman Province and Kunar Province. Its administrative center, Parun, is located in the Parun valley. Before 2001 its administrative center was situated in Laghman province due to Mujahideen control over Nuristan province.

The primary occupations are agriculture, animal husbandry, and day labor. Located on the southern slopes of the Hindu Kush mountains in the northeastern part of the country, Nuristan spans the basins of the Alingâr, Pech, Landai Sin, and Kunar rivers. It is bordered on the north by Badakhshan Province, on the south by Laghman and Kunar provinces, on the west by Panjshir Province, and on the east by Pakistan.

The Kalasha (Kalasha: Kaĺaśa, Nuristani: Kasivo) or Kalash, are indigenous people residing in the Chitral District of Khyber-Pakhtunkhwa province of Pakistan. They speak the Kalasha language, from the Dardic family of the Indo-Iranian languages, and are considered a unique tribe among the Indo-Aryan peoples of Pakistan.

They are related to the Nuristani people of the adjacent Nuristan (historically known as Kafiristan) province of Afghanistan. An autochthonous and polytheistic group like the Kalasha of Chitral, the Nuristani were forcibly converted to Islam by the 'Iron Amir' Abdur Rahman Khan in the late 19th century, while the Kalasha of Chitral maintain their own separate cultural traditions.

According to the linguist Richard Strand, the people of Chitral apparently adopted the name of the former Kafiristan Kalasha, who at some unknown time extended their influence into Chitral.^{[citation needed]}