The site of the present-day abbey was probably occupied as early as the 5th century by Breton immigrants from across the Channel, perhaps disciples of Saint Conogan [fr], but nothing remains of the original buildings.

Notre-Dame de Langonnet Abbey was founded on June 20, 1136 by Conan III, sovereign duke of Brittany, and his mother Ermengarde of Anjou.

A confession dated 1550 attests that the abbey owned 82 villages, manors, noble holdings, mills and forests, including 63 in Langonnet, 14 in Gourin and 5 in Le Faouët.

In 1170, Duke Conan IV gave the abbey's Cistercian monks several villages near the Carnoët forest to establish a community.

It was largely rebuilt between 1650 and 1780: "The main body of the abbey is a large square building, of which the church occupies one side; most of this building was constructed in the time of the abbot commendataire Claude de Marbœuf" (an inscription Aeternitati positum [built for eternity] gives the date 1688), "the church is the newest part, built by abbé François Chevreul and dedicated in 1789".

It soon became a refuge for the Chouans, who were dislodged by a detachment of republican soldiers from Le Faouët, who vandalized the premises and took up residence there to keep watch over the surrounding area.

[2] By decree of June 10, 1806, Napoleon I established Brittany's first public stud farm with forty stallions and ten brood mares.

Its position is very advantageous, in the middle of beautiful meadows watered by the lovely Ellé river, and surrounded by a walled park.

As the abbey was falling into ruin, the translation of the precious relic to the Abbaye Notre-Dame de Langonnet on August 7 and 8, 1880, in the presence of the bishops of Quimper and Vannes, 150 priests and 20,000 devotees.

"The old missionaries reside there, to put an interval between their life of action and supreme rest; there, in an apostolic school, are formed the children who will later perpetuate the lineage" wrote Georges Goyau in 1936.

[2] Sam Poupon founded the cercle de l'abbaye in 1950 (Korollerien an Ellé), one of the first (after the Poullaouen group) to revive Breton dance.

The chapter house, surrounded by buildings dating from the modern era, is the only vestige dating back to the 13th century: "it has an ogival doorway overlooking the cloister, flanked on either side by twin bays, all with a lancet arch, with several recesses formed by toroids falling on columns with bases and leafy capitals; each of the double bays is also framed by an arcade, also ogival.