The term « Saint Peter in Chains » refers to the imprisonment of the Apostle Peter, in Jerusalem, by King Herod Agrippa, in the year 43.
The commemoration is celebrated on August 1st.
A first church, which became too small, was located in Le Plagnol, the oldest district of the village, until the 18th century.
The new church, much larger at 28 meters long, was built in 1705 in the lower part of the village, with a nave and two chapels in front of the choir.
The church was severely damaged by two successive floods of the Garonne River, particularly in 1772.
Reconstruction lasted until 1781.
Despite the modesty of the church’s exterior, the rich interior decorations reflect the interest then shown in FOS, the first large town at the gateway to the Kingdom of France.
A carved and gilded wooden altar was built, topped with a round colonnade with frieze and canopy.
The apse has been listed as a historical monument since 1986.
In 1856, the two chapels were extended to the bell tower to increase capacity.
But in 1907, ground movements required reinforcement work and the removal of the north aisle,
resulting in the asymmetry visible from the outside.
The 2013 flood caused no damage. Only the floor was covered by 20 cm of water.
The baldachin, placed on colonnades with Corinthian capitals (late 18th-century neoclassicism), rises to 7.60 meters.
The top of the baldachin is supported by inverted consoles resting on friezes, painted in the « royal blue » of the French Guards regiment uniform.
The whole structure, blessed on December 8, 1781, is the work of the great 18th-century baroque sculptor: Dominique Ferrère.
The ceiling painting, adorned with a neoclassical frieze, depicts the apotheosis of Saint Peter, Patron of FOS.
The mural paintings of the altar of the Chapel of the Virgin (to the right of the altar) date from the early 20th century (1900–1910), during the last renovation.
The stained glass windows were then made thanks to donations from people of the commune.
At the church of FOS, the painting « The Child Jesus Found in the Temple » was bequeathed, painted by the famous Jacques STELLA (1596–1657), court painter and student of Nicolas Poussin.
This painting is now the property of the commune of FOS. It is on display, on deposit, at the treasury of the neighboring village of Saint Béat.
The altar, in carved and gilded wood, is decorated with two little angels on the front corners and two adoring angels on the lower part, in the pure style of Pyrenean baroque.
Avenir du passé 