Langenthal is first mentioned in 861, as marcha in Langatun, referring to farming estates scattered along the Langete (a tributary of the Murg).

The Old High German name Langatun is presumably composed of a hydronym langa- and the Gaulish element dunum "fort" (which had become productive as a suffix in toponyms).

[5] The re-interpretation of the name as including the element -tal "valley" dates to c. the 15th century, during which the name is on record as either Langaten or Langental (the same process can be observed in the case of Murgenthal, earlier Murgatun).

The establishment of the Abbey brought agricultural improvements, especially the introduction of an irrigation system to the area.

However, the Abbey often came into conflict with the Kyburg Ministerialis (unfree knights in the service of a feudal overlord) family of Luternau.

Just a few years later, in 1279, the Abbey, in turn, was forced to give the low court and a fortified house in Langenthal to the Freiherr of Grünenberg to hold as a fief.

By the end of the 14th century, the Abbey had regained power and was able to bring the village fully under their control.

In 1415, Langenthal became incorporated into the territory of the Republic of Bern, but it remained under the landlordship and the low court of the monastery.

The Protestant Reformation of 1528 weakened the power of the Abbey slightly, but it continued to collect tithes and appoint the village priest until Bern bought those rights in 1808.

By 1616 Langenthal had a series of laws and regulations governing the booming markets and trade in the town.

In 1640 Langenthal and Langnau became centers of linen canvas production and export to France, Italy, Spain and Portugal.

In 1704 Langenthal became the seat of the Oberaargau canvas dealer's guild, which brought together weavers, shopkeepers and traders to protect their interests.

The decline of eastern Switzerland's linen industry in the 18th century gave Langenthal a further boost, which encouraged to Bern to tighten supervision.

Beginning in 1758 the Bernese government started inspecting cloth for quality and controlling who was allowed to sell.

Even though the Aargau cantonal road bypassed the Langenthal, by 1756 it had grown to a total of 189 households, three taverns, various administrative buildings and a warehouse (dated 1748).

The market street was paved in 1730 and the Langete was partially covered with stone bridges and new houses.

A small elite of merchants, lawyers, physicians and pharmacists emerged and turned Langenthal into a center of the liberal and nationalist thought during the early modern era.

Langenthal had been a subject territory of Berne within the Old Swiss Confederacy since 1415, and tended to support uprisings against the central authorities; during the Swiss peasant war of 1653 Langenthal had supported the peasant uprising, as well as the 1798 French invasion and the liberal Helvetic Republic.

[6] The current municipal coat of arms, three wavy bands in blue on yellow (Or three Bends wavy Azure), has been in use since c. 1870, replacing an earlier design in red and silver,[7] but the use of a flag with a similar design, "yellow and blue with a triple rivulet" (Sie führen einen Fahnen ist gälb und blaw / In dreyfachen Bach darinnen) is recorded in a song of c. 1700.

Langenthal's location on the road from Bern to Zurich (completed in 1760) and on the Swiss Central Railway line (inaugurated in 1857) spurred industrial development, led by textiles and machines.

In 2001, Langenthal was twinned with the town of Neviano in southern Italy and with Brig-Glis in the upper Valais.

Of the rest of the land, 4.96 km2 (1.92 sq mi) or 34.4% is settled (buildings or roads), 0.04 km2 (9.9 acres) or 0.3% is either rivers or lakes.

17.7% of the total land area is heavily forested and 3.2% is covered with orchards or small clusters of trees.

The old village of Langenthal and the hamlet of Chlyrot are part of the Inventory of Swiss Heritage Sites.

In the tertiary sector; 2,119 or 37.6% were in wholesale or retail sales or the repair of motor vehicles, 317 or 5.6% were in the movement and storage of goods, 259 or 4.6% were in a hotel or restaurant, 152 or 2.7% were in the information industry, 303 or 5.4% were the insurance or financial industry, 453 or 8.0% were technical professionals or scientists, 317 or 5.6% were in education and 1,170 or 20.8% were in health care.

[15] The local Muslim community was at the time in the process of planning a minaret for their "cultural centre" in 2009.

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

The first of these is a major interchange, with regular service to Zürich Hauptbahnhof, Bern, Solothurn, Baden, Lucerne, and Olten.