Porrentruy (French: [pɔʁɑ̃tʁɥi]; Franc-Comtois: Poérreintru [pweʁɛ̃tʁy]; German: Pruntrut) is a Swiss municipality and seat of the district of the same name located in the canton of Jura.

The first trace of human presence in Porrentruy is a mesolithic tool that was found in the backyard of the Hôtel-Dieu.

In 1983, the ruins of a Gallo-Roman temple were discovered in the cemetery on the north of town, and Roman coins were found there.

Near the town, a kilometre long (0.6 mile) section of the Augst-Epomanduodurum (now Mandeure) Roman road was discovered.

[4]: 231  The German form of the name, Pruntrut may have a separate etymology from Bruntrutum, which means an abundant spring.

The Counts of Pfirt, who owned the region around Porrentruy, built a castle on a defensible hill and made it the capital of the Ajoie territory.

A settlement (now known as the Faubourg de France) was founded at the foot of the castle, with another south on the opposite hill.

The Counts of Montbéliard refused to hand over Porrentruy, which led Bishop Henry of Isny to request support from King Rudolph I of Habsburg.

On 20 April 1283, the king asked the Bishop of Basel to grant Porrentruy a town charter and make it a free Imperial city.

[3] Financial difficulties forced the Bishop to sell the Ajoie (including Porrentruy) back to the lords of Montbéliard in 1386.

[5] Under Bishop Jakob Christoph Blarer von Wartensee, who reigned from 1575 to 1608, the town reached the apogee of its importance.

In his time, many architectural projects, including expansion of the castle and the building of a Jesuit college, were undertaken.

Several religious orders were active in the city, including the Jesuits who built their college in 1591.

In addition to the Jesuits other orders included the Ursulines (1619), the Sisters of the Annonciade (permanently established in 1646) and the Capuchins (1663).

Porrentruy became the capital of a dependent republic, which was then incorporated into France in 1793 as the Département du Mont-Terrible.

During the War of the Sixth Coalition against Napoleon, Allied troops entered Porrentruy on 24 December 1813.

The political life in the 19th century was characterized by the severe conflict between Liberal-Radicals and the Catholic Conservatives.

The secular side gained power in 1860, when the mayor, Joseph Trouillat, was forced out of office.

[3]+On April 24, 1917, the Swiss town of Porrentruy was mistakenly shelled by German artillery during World War I.

The artillery fire originated from German positions located near the French border, specifically around Delle, which is approximately 5 to 10 kilometers from Porrentruy.

The bombardment was an unfortunate mistake, as German forces were targeting nearby military positions but inadvertently struck neutral Swiss territory.

Until World War I, Porrentruy was the cultural center of the region and had a larger population than Delémont.

However, with the increase in automobile traffic, its situation on the edge of the country became a liability and caused economic stagnation.

[7] The municipality lies on both sides of the Allaine River, in Ajoie (the bulge in the northwest corner of Switzerland that extends into France) at the foot of the Jura Mountains on the north.

[11] The historical population is given in the following chart:[3][15] The Archives of the Republic and the Canton and the cantonal library, Porrentruy Castle, the church and college of the Jesuits, the St-Pierre Church, the Hôtel de Gléresse et Fondation des Archives, the Hôtel de Gléresse with the archives, the Hôtel-Dieu with the Pharmacy Museum and the Jura Natural Sciences Museum and gardens are listed as Swiss heritage site of national significance.

In the 20th century, other important industries were added, notably metalworking, machine manufacturing, electronics, and furniture building.

In the tertiary sector; 612 or 21.1% were in wholesale or retail sales or the repair of motor vehicles, 65 or 2.2% were in the movement and storage of goods, 133 or 4.6% were in a hotel or restaurant, 22 or 0.8% were in the information industry, 163 or 5.6% were the insurance or financial industry, 220 or 7.6% were technical professionals or scientists, 340 or 11.7% were in education and 834 or 28.7% were in health care.

This is followed by three years of obligatory lower secondary school where the students are separated according to ability and aptitude.

[28] The municipality lies on the first stretch of the motorway (A16 or E27) to open (in 1998) in the canton of Jura between Delémont and Belfort, France.

The motorway is meant to be completed in 2016, the difficult topography of the Jura only allowing the opening of short sections, one by one.