The diocese is suffragan to the Archdiocese of Reims and corresponds, with the exception of two hamlets, to the entire Department of Aisne.

[1] In the 280's the Caesar Maximian, the subordinate of the Emperor Diocletian, and his Praetorian Prefect Riccius Varus[2] campaigned in northeast Gaul and subdued the Bagaudae, an event accompanied by much slaughter.

It was the capital of the Kingdom of Soissons, a remnant of the Roman Empire in northern Gaul, and remained one of the chief cities under King Clovis I.

Hilduin, abbot (822–30), in 826 obtained from Pope Eugene II relics of St. Sebastian and St. Gregory the Great; he caused the relics of St. Godard and St. Remi to be transferred to the abbey; he rebuilt the church which was consecrated 27 August 841, in the presence of Charles the Bald and seventy-two prelates.

Bishop Rothadus of Soissons was deposed, due to the malevolence of Archbishop Hincmar of Reims, but restored on orders of Pope Nicholas I.

The Benedictine Abbey of Note Dame de Soissons was founded in 660 by Ebroin and his wife Leutrude.

Among its earlier monks were: St. Gobain, who, through love of solitude, retired to a desert place near Oise and was slain there; St. Chagnoaldus, afterward Bishop of Laon, who wished to die in his monastery; St. Humbert, first abbot of Maroilles in Hainaut.

The Abbey of St. John at Laon was founded in 650 by St. Salaberga, who built seven churches there; she was its first abbess; St. Austruda (d. 688) succeeded her.

In the Diocese of Soissons, the Premonstratensians had the abbeys: Chartreuve, Valsery, Saint-Yved de Braine, Villers Cotterets, Val Secret, Vauchrétien, Lieurestauré.

Abbott Fulrade built the Church of St-Quentin in the eighth century and Pope Stephan II blessed it (816).

During the Middle Ages a distinct type of religious architecture sprang up in Soissons; Eugéne Lefèvre Pontalis has recently brought out a work dealing with its artistic affiliations.

After investigation Canon Bauxin concludes that the cathedral of Laon, as it exists, is not the one consecrated in 1114 and visited by Innocent II in 1132; that was the restored ancient Romanesque building; the present one was built 1150–1225.

Among the natives of the diocese may be mentioned: Petrus Ramus (1515–72), Jean Racine (1639–99), La Fontaine (1621–95), Luc d'Achery (1609–1685), Charlevoix (1683–1761), Camille Desmoulins (1760–1794).