[1] The cathedral is said to have been built atop the foundations of a chapel constructed in the 3rd century by Saint Saturnin, sent to Christianize the Gauls and martyred in Toulouse.

The new bishop, Bertrand de L'Isle-Jourdain, quickly adopted the High Gothic and Rayonnant style established in northern France.

In about 1272, he commissioned a new architect, probably Jean Deschamps, who was building Narbonne Cathedral, to construct the new choir in the northern style.

[3] Pierre de Moulin (1439–51) modified the grand portal of the nave, destroying the major part of the west front of the 13th century church.

To this end he raised the pillars and buttresses on the south side of the choir, with an abundance of decoration in the Flamboyant Gothic style.

The emotions caused by the fire inspired a fund-raising campaign from the public and local government to complete the cathedral.

He added height to buttresses and put in place flying arches to support the higher walls and vaults.

This was less than the grand church planned by Bertrand de l'Isle, but the new exterior walls gave it the impression of greater height.

[4] In 1790, shortly after the outbreak of the French Revolution, the chapter of the choir was abolished, and a number of the funeral monuments in the interior were destroyed.

The sculpture of the tympanum depicting Christ blessing the world was replaced by a plaque declaring "Temple of Reason".

The statues of the apostles, of Saint Stephen and of the Archbishops Pierre and Denis du Moulon were hammered to pieces.

In 1794 and 1795, the cathedral served as a collection point for iron and other metal objects, notably the bells taken from all of the surrounding churches.

The Chapel of the Relics was restored by Auguste Virebent from 1842 to 1847, and the retable of the altar of the Paris was remade in 1847–1848 in the neo-Gohic style, with elements of sculpture copied from earlier works.

In 1864 Cardinal Deprez received permission to hold a lottery to raise the money for the demolition of the old nave and the construction of a new building, but the plan was not carried out.

Finally, in 1911, the chief architect of Historic Monuments, Auguste Saint-Anne de Louzier, proposed a compromise which was accepted.

The irregular west front exists because the cathedral consists of two incomplete churches of different periods, awkwardly put together.

The new, more ornate northern French Gothic style was introduced to fight Cathar heresy through preaching and more dramatic and inspiring architecture.

[7] The early bell tower, combined with a fortress-like donjon, was built in on the north side of the west front.

The ribs of the vaults are supported by columns set into the walls and decorated with carved capitals depicting Biblical scenes.

By all appearances, the original intent was to demolish the old nave, and replace it with a new structure aligned with and in a similar style to the choir.

Early in the 16th century, the bishop Jean d'Orleans launched a project to lengthen and finish the choir and construct a full transept.

In order to rebuild it more quickly, the plans were revised, and the vaulted ceiling of the choir was given a height of only 27 meters, far lower than the original design.

To compensate for the more modest architecture, the choir was given an extremely imposing main altar, designed between 1667 and 1670 by the architect Pierre Mercier and the sculptor Gervais Drouet.

One section of the royal window in a chapel was purchased by the American newspaper publisher and art collector William Randolph Hearst, and is now in Forest Lawn Memorial Park, a cemetery.

There are one hundred fourteen stalls, in the style of the period of Louis XIII, made between 1610 and 1613, placed on both sides of the choir.

The cathedral has a large collection of paintings illustrating biblical themes, located in the chapels around the choir and in the nave.

Several works of the 18th-century Toulouse painter Jean-Baptiste Despax (1710–1773), including "Solomon holding the plans of Jerusalem", are also found in the cathedral.

Placed behind the altar, the retable has three levels of sculpture, depicting the stoning of Saint Stephen, the first Christian martyr.

Today the bells can also be rung by a small electronic keyboard, located in the sacristy at the opposite end of the cathedral.

It rises seventeen meters above the floor, suspended from the wall just below the vaults, resting on a small ledge, in what is called "The swallow's nest" ("Nid de Hirondelle").