The diocese was originally part of the
Diocese of Thérouanne, which had been established in the 7th or 8th century. In 1553
Charles V, Holy Roman Emperor besieged the city of
Thérouanne, then a French enclave in the
Holy Roman Empire, in revenge for a defeat by the French at
Metz. After he captured Thérouanne, he razed the city. In 1557, as a result of the war damage to its see, the diocese was abolished. This led to a reform of sees at the
Council of Trent and the bishopric of Thérouanne was split between the
Diocese of Saint-Omer, the
Diocese of Boulogne and the Diocese of Ypres. With this,
Saint Martin's Church was elevated to cathedral status, as it became the see of the new diocese. After the
Concordat of 1801 between
Napoleon and
Pope Pius VII, Ypres was incorporated into the
Diocese of Ghent, and Saint Martin's lost its status as a cathedral.
Cornelius Jansen, the father of the theological movement
Jansenism, was Bishop of Ypres from 1635 to 1638. ==Bishops==