Münsingen is a municipality in the Bern-Mittelland administrative district in the canton of Bern in Switzerland. On 1 January 2013 the former municipality of Trimstein merged into the municipality of Münsingen.
Münsingen developed from a Celtic village first settled in around 400 BC. The origin of the name is unclear, though attributed to the Alamanni. During the early and middle La Tene era the residents of the village built about 220 tombs along the Aare river. Some of the men were buried with their weapons and the women and children were buried with jewelry. A total of 1,200 items were discovered from the village. The rich collection of artifacts and the clear stratigraphic layers at Münsingen have helped archeologists to develop a model for dating isolated graves from Germany to Romania to Italy. The relatively small number of individuals combined with the rich grave goods indicate that the settlement at Münsingen was home to Celtic nobility. Two of the graves contain skulls that show evidence of trepanation or holes bored into the skull.
During the Roman era there was a country estate or very small settlement near where the village church stands today. Scattered fragments of a wall and a bath house have been discovered. The bath house floor was decorated with mosaics depicting fishes and the god Oceanus. The bath house is probably from the 2nd century AD.
Münsingen is first mentioned between 993 and 1010 as Munisingam when King Rudolph III of Burgundy granted it to Count Kuno. It passed through the hands of the Kyburgs and the Zähringens. Then, in the 13th and 14th centuries Münsingen came under the lordship of the Senn knights from whom the present arms of the municipality are derived. In 1377, the last member of the family sold the town to a wealthy family in Bern. It passed through several families before the city of Bern gradually acquired all the rights to the town.
As an important gathering-place during the Peasants' War, and in the ensuing process of democratization, Münsingen played a major part in the history of the canton of Bern.
Originally, the town was ruled from a castle located on the heights above the Müli valley. However, this building fell into ruin and little is known about it. By the 12th century another castle was built in Münsingen town. The Senn family ruled the town from this castle. However, it was demolished by Bern in 1311. A wooden outbuilding was built on the castle lands three years later, in 1314. In 1550 the Schultheiss Hans Franz Nägeli rebuilt the castle building into Münsingen Castle. It was renovated and repaired in 1749-53. In 1977 the municipality acquired the castle and converted it into a municipal museum. The wooden outbuilding was rebuilt in 1570 into a country estate house by the Schultheiss Johannes Steiger. It was purchased in 1877 by the Canton of Bern and converted into a cantonal psychiatric clinic.