Alta (Norwegian: [ˈɑ̂ɫtɑ] ^ⓘ; Northern Sami: Áltá [ˈaːlːhtaː]; Kven: Alattio; Finnish: Alattio) is the most populated municipality in Finnmark county, Norway. The administrative centre of the municipality is the town of Alta. Some of the main villages in the municipality include Kåfjord, Komagfjord, Kvenvik, Langfjordbotn, Leirbotn, Rafsbotn, Talvik, and Tverrelvdalen.

The town of Alta and most of the municipality is located just below the 70th latitude and is closer to the North Pole than it is to much of Central Europe and the British Isles. The town is the northernmost settlement of urban significance in the European Economic Area, with municipalities north of Alta being sparsely populated. In spite of its high latitude the local climate is seldom severely cold thanks to Gulf Stream moderation in the prevailing wind, and lower altitudes of the municipality are covered with boreal forests. Due to Norway curving above its Nordic neighbours, Alta is located further east than almost all of Sweden and much of southern Finland. Being at a very high latitude, midnight sun and polar night are present for sizeable parts of the year.

The 3,849-square-kilometre (1,486 sq mi) municipality is the 7th largest municipality by area out of the 357 municipalities in Norway. Alta is the 59th most populous municipality in Norway with a population of 21,708. The municipality's population density is 5.6 inhabitants per square kilometre (15/sq mi) and its population has increased by 9.5% over the previous 10-year period.

The old Alten-Talvig Municipality was established on 1 January 1838 (see formannskapsdistrikt law). Not long afterwards, on 1 January 1863, it was divided into two: Talvik Municipality to the north (population: 1,938) and Alta Municipality to the south (population: 2,442). On 1 January 1964, the two neighboring municipalities were merged back together to form a new Alta Municipality. Prior to the merger, Alta had 6,629 residents and Talvik had 3,266 residents. The borders have not changed since that time.

On 1 January 2020, the municipality became part of the newly formed Troms og Finnmark county. Previously, it had been part of the old Finnmark county. On 1 January 2024, the Troms og Finnmark county was divided and the municipality once again became part of Finnmark county.

The municipality (originally the parish) is named after the local Altafjorden. The name possibly comes from the Old Norse words ǫlpt or alpt which refer to a swan. It could also be the Norwegianization of the Finnish word (alaattia) which refers to a "lowland". Historically, the name of the municipality was spelled Alten. On 3 November 1917, a royal resolution changed the spelling of the name of the municipality to Alta.

The coat of arms was granted on 9 July 1976. The official blazon is "Azure, a spearhead argent" (Norwegian: I blått en hvit spydspiss). This means the arms have a blue field (background) and the charge is a spear head. The spear head has a tincture of argent which means it is commonly colored white, but if it is made out of metal, then silver is used. The blue color in the field symbolizes the local river, sea, and mountains. The spear head is derived from the findings of quartzite spear heads dating back to the late Stone Age and found in the area. The quartzite was quarried in the municipality and tools made from it were used all over Northern Norway.

The Church of Norway has two parishes (sokn) within Alta Municipality. It is part of the Alta prosti (deanery) in the Diocese of Nord-Hålogaland.