Even if it hasn't yet been proven, it is likable that a few people were already installed on the rock overhanging the River Sarthe during the Roman occupation. In the VIth Century, around ten families were registered on the site called Faxinidum.

The city history really begins with the erection of the castle, which were initiated approximately in the Xth Century (perhaps in IXth Century), under the reign of King "Charles le Chauve". Express mention can be found on an official document dated October 12, 997, first year of the reign of King "Robert the Pieux". The purpose of the castle was mostly to ensure protection of the river crossing.

Guillaume le Conquérant captured twice the castle : first time in 1063, then again in 1073. Young "Robert de Bellême", that particularly illustrated himself during the siege, was proclaimed as a knight from Guillaume's hand.

In 1100, Henri the First decided to join the Maine to the Anjou. The castle then became part of a series of several, destinated to protect the Maine against "North Mans" (Vickings)'s attacks, and the city was placed under the protection of the Vicomte de Beaumont. At that time, the city was then called Fresnay-le-Vicomte. A few more attacks were conducted against Fresnay, and the city finally recoved peace only at the beginning of the XIVth Century. That period permitted the development of farming.

Strategic importance of the Castle of Fresnay was particularly highlighted during the "Guerre de 100 ans" (100 years War). Successively occupied by the adventurers of Philippe de la Chèze, in 1356, then captured by the British troups of King Henri V, in 1417, it came back to French, thanks to Ambroise de Loré, future companion of Jane Of The Arc; Captain of the Castle in 1418 he later became "Prévôt" de Paris.

In 1420, the city was again taken by English that occupied the place for thirty years (1420 to 1450). Heavily affected by the "Guerre de 100 ans", she also had to suffer from Religion Wars; in 1652, she was devastated by "The Huguenots". From then, the castel started to gradually fall in ruins.

From the Beginning of XVIIth Century until the end of the XIXth Century, culture of the hemp considerably growth; that textile was especially used for the sails. New quarters were created in Fresnay's area : the "Bourg-Neuf" and the "Creusot". Some weaver's houses remain actually visible. In 1793, the old wooden bridge were replaced by one made in stones.

During the XXth Century, weaving workshops were replaced by agronomics and domestic appliances industries.

As from last cencus data (1999), 2 363 persons live in Fresnay (the "Fresnois"); the city is the center of a dozen rural districts, now grouped in a "Alpes Mancelles Rural Districts Community", that leads to 8 000 the total of people leaving in the region.