Undervelier is a former municipality in the district of Delémont in the canton of Jura in Switzerland. On 1 January 2013 the former municipalities of Bassecourt, Courfaivre, Glovelier, Soulce and Undervelier merged to form the new municipality of Haute-Sorne.
Undervelier is first mentioned in 1179 as Undreviller. The municipality was formerly known by its unknown name Underswiler, however, that name is no longer used.
Undervelier had an area of . Of this area, or 24.2% is used for agricultural purposes, while or 73.3% is forested. Of the rest of the land, or 2.1% is settled (buildings or roads), or 0.1% is either rivers or lakes and or 0.2% is unproductive land.
Of the built up area, housing and buildings made up 1.1% and transportation infrastructure made up 0.9%. Out of the forested land, 70.7% of the total land area is heavily forested and 2.6% is covered with orchards or small clusters of trees. Of the agricultural land, 2.8% is used for growing crops and 13.5% is pastures and 7.7% is used for alpine pastures. All the water in the municipality is flowing water.
The former municipality is located in the Delemont district, between two of the Sorne river canyons and at the foot of Pichoux mountain.
The blazon of the municipal coat of arms is Or three Piles issuant from sinister shortened Sable.
Undervelier had a population () of 296. , 10.5% of the population are resident foreign nationals. Over the last 10 years (2000–2010) the population has changed at a rate of -4.6%. Migration accounted for 2.8%, while births and deaths accounted for -3.7%.
Most of the population () speaks French (258 or 80.4%) as their first language, German is the second most common (49 or 15.3%) and Italian is the third (7 or 2.2%).
the population was 50.0% male and 50.0% female. The population was made up of 136 Swiss men (44.2% of the population) and 18 (5.8%) non-Swiss men. There were 142 Swiss women (46.1%) and 12 (3.9%) non-Swiss women. Of the population in the municipality, 135 or about 42.1% were born in Undervelier and lived there in 2000.